Sync error "server.authenticationToken.internalError"


I am having problems getting my library to sync and cant find the solution online. I have tried re-entering my password in the sync settings and know my password is correct as I tested it on the web version. Can anyone help? Here is my error code: 

Sync Details
Sync was last run: Monday, November 05, 2018 at 21:27:02 PM +1100
Sync Status: There are changes that need to be sent.
Error Code: Server.AuthenticationToken.internalError
Error Message: The username/password specified is not valid.

Local Sync Library
Library Name: My EndNote Library.enl
References: 559
Groups: 11
Group Sets: 2
Attachments: 434

Online Sync Library
Serial Number: 3091850001 (Premium until August 01, 2019)
References: 560
Groups: 11
Group Sets: 2
Attachments: 434 (333.53 MB)

Sync Limits
Number of References: 1000000 (999440 can still be added)
Number of Groups: 5000 (4989 can still be added)
Number of Group Sets: 5000 (4998 can still be added)
Attachment Storage: Unlimited


Please contact Technical Support directly

1-800-336-4474 option 4 then 1


For anyone having the same problem this worked for me:

I opened EndNote-Online through the desktop version of Endnote (Help/EndnoteOnline) and logged in. 

Went back to the Endnote desktop version and opened Sync-preference (Edit/Preferences…/Sync) and re-entered my password. Then pressed “Use”, and closed the preferences.

Now the sync worked again…

Not sure what caused this to work but i did…

Setup: PC, Windows 10, Endnote X9