diff --git a/core/service.go b/core/service.go
index 4e7d612..0058d0b 100644
--- a/core/service.go
+++ b/core/service.go
@@ -322,7 +322,7 @@ func (sh *serviceDescription) link(w http.ResponseWriter, r *http.Request) {
 	if !guestlink {
 		_, err = sh.readProfile(oldType, oldId, bfinfo)
 		if err != nil {
-			logger.Error("readProfile(old) failed :", err)
+			logger.Println("readProfile(old) failed :", err)
 			w.WriteHeader(http.StatusBadRequest)
 			return
 		}
@@ -332,7 +332,7 @@ func (sh *serviceDescription) link(w http.ResponseWriter, r *http.Request) {
 
 	oldType, oldId, err = sh.getProviderInfo(oldType, oldId)
 	if err != nil {
-		logger.Error("getProviderInfo failed :", err)
+		logger.Println("getProviderInfo failed :", err)
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
@@ -346,7 +346,7 @@ func (sh *serviceDescription) link(w http.ResponseWriter, r *http.Request) {
 
 	email, err := sh.readProfile(newType, newId, bfinfo)
 	if err != nil {
-		logger.Error("readProfile(new) failed :", err)
+		logger.Println("readProfile(new) failed :", err)
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
@@ -359,7 +359,7 @@ func (sh *serviceDescription) link(w http.ResponseWriter, r *http.Request) {
 
 	newType, newId, err = sh.getProviderInfo(newType, newId)
 	if err != nil {
-		logger.Error("getProviderInfo failed :", err)
+		logger.Println("getProviderInfo failed :", err)
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
@@ -390,7 +390,7 @@ func (sh *serviceDescription) link(w http.ResponseWriter, r *http.Request) {
 	}, options.Update().SetUpsert(true))
 	if err != nil {
 		logger.Error("link failed. Update ServiceName err :", err)
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 
@@ -457,7 +457,7 @@ func (sh *serviceDescription) unlink(w http.ResponseWriter, r *http.Request) {
 
 	sType, sId, err := sh.getProviderInfo(sType, sId)
 	if err != nil {
-		logger.Error("getProviderInfo failed :", err)
+		logger.Println("getProviderInfo failed :", err)
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
@@ -476,7 +476,7 @@ func (sh *serviceDescription) unlink(w http.ResponseWriter, r *http.Request) {
 
 	if err != nil {
 		logger.Error("unlink failed, fail to count accounts :", err)
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusInternalServerError)
 	}
 
 	if len(accDocs) <= 1 {
@@ -505,7 +505,7 @@ func (sh *serviceDescription) unlink(w http.ResponseWriter, r *http.Request) {
 	}, options.FindOneAndDelete().SetProjection(bson.M{"_id": 1}))
 	if err != nil {
 		logger.Error("unlink failed. Delete ServiceName err :", err)
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 	if preid == nil {
@@ -554,7 +554,7 @@ func (sh *serviceDescription) linkinfo(w http.ResponseWriter, r *http.Request) {
 
 	sType, sId, err := sh.getProviderInfo(sType, sId)
 	if err != nil {
-		logger.Error("getProviderInfo failed :", err)
+		logger.Println("getProviderInfo failed :", err)
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
@@ -574,7 +574,7 @@ func (sh *serviceDescription) linkinfo(w http.ResponseWriter, r *http.Request) {
 	}))
 	if err != nil {
 		logger.Error("linkinfo failed. CountDocuments err :", err)
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 
@@ -588,6 +588,11 @@ func (sh *serviceDescription) linkinfo(w http.ResponseWriter, r *http.Request) {
 	}, options.Find().SetLimit(sh.MaximumNumLinkAccount).SetProjection(bson.M{
 		platformName: 1,
 	}))
+	if err != nil {
+		logger.Error("linkinfo failed. FindAll returns err :", err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
 
 	var linkstrs []string
 	for _, link := range links {
@@ -597,7 +602,7 @@ func (sh *serviceDescription) linkinfo(w http.ResponseWriter, r *http.Request) {
 	linkbytes, err := json.Marshal(linkstrs)
 	if err != nil {
 		logger.Error("linkinfo failed. json marshal fail :", err)
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 
@@ -630,29 +635,29 @@ func (sh *serviceDescription) authorize(w http.ResponseWriter, r *http.Request)
 			//email, err := sh.readProfile(authtype, uid, accesstoken)
 			bfinfo, err := sh.getUserBrowserInfo(r)
 			if err != nil {
-				logger.Error("getUserBrowserInfo failed :", err)
+				logger.Println("getUserBrowserInfo failed :", err)
 				w.WriteHeader(http.StatusBadRequest)
 				return
 			}
 
 			email, err = sh.readProfile(authtype, uid, bfinfo)
 			if err != nil {
-				logger.Error("readProfile failed :", err)
+				logger.Println("readProfile failed :", err)
 				w.WriteHeader(http.StatusBadRequest)
 				return
 			}
 
 			newType, newId, err := sh.getProviderInfo(authtype, uid)
 			if err != nil {
-				logger.Error("getProviderInfo failed :", err)
+				logger.Println("getProviderInfo failed :", err)
 				w.WriteHeader(http.StatusBadRequest)
 				return
 			}
 
 			if authtype != newType || uid != newId {
+				logger.Printf("auth success ( redirect ) : %s->%s, %s->%s, %s, %s", authtype, newType, uid, newId, email, session)
 				authtype = newType
 				uid = newId
-				logger.Println("auth success ( redirect ) :", authtype, uid, email, session)
 			}
 		} else {
 			email = fmt.Sprintf("%s@guest.flag", uid)
@@ -733,6 +738,8 @@ func (sh *serviceDescription) authorize(w http.ResponseWriter, r *http.Request)
 			return
 		}
 
+		logger.Println("session created :", accid, authtype, uid, email, newsession)
+
 		output := map[string]any{
 			"sk":         newsession.Hex(),
 			"expirein":   sh.sessionTTL.Seconds(),
@@ -757,8 +764,7 @@ func (sh *serviceDescription) authorize(w http.ResponseWriter, r *http.Request)
 					},
 				}, options.Update().SetUpsert(false))
 			if err != nil {
-				logger.Error("update auth collection failed")
-				logger.Error(err)
+				logger.Error("update auth collection failed :", err)
 				return
 			}
 
@@ -773,6 +779,9 @@ func (sh *serviceDescription) authorize(w http.ResponseWriter, r *http.Request)
 				"sk":       session,
 				"expirein": sh.sessionTTL.Seconds(),
 			}
+
+			logger.Println("session updated :", authtype, uid, session)
+
 			bt, _ := json.Marshal(output)
 			w.Write(bt)
 		} else {
@@ -850,14 +859,14 @@ func (sh *serviceDescription) delacc(w http.ResponseWriter, r *http.Request) {
 	delaccnum, err := sh.mongoClient.DeleteMany(CollectionAccount, delfilter)
 	if err != nil {
 		logger.Error("delacc failed. Delete many CollectionAccount err :", err)
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 
 	_, err = sh.mongoClient.DeleteMany(CollectionLink, delfilter)
 	if err != nil {
 		logger.Error("delacc failed. Delete many CollectionLink err :", err)
-		w.WriteHeader(http.StatusBadRequest)
+		w.WriteHeader(http.StatusInternalServerError)
 		return
 	}
 
@@ -964,7 +973,7 @@ func (sh *serviceDescription) serveHTTP(w http.ResponseWriter, r *http.Request)
 				}
 			}
 		} else {
-			logger.Println("div is not found :", divname)
+			logger.Println("div is not found :", divname, sh.Divisions)
 			w.WriteHeader(http.StatusBadRequest)
 		}
 	} else {