Sim Link signed out by itself… I have this problem a few day…
Dear user,
Kindly ensure that your system’s time and timezone are automatically synced with the internet.
Please let us know if you encounter any issues.
Best regards,
Vishal Ahir
Navigraph
Hi there.
I’m encountering the same issue for a few days now.
I sign in OK, it signs out immediately in Simlink. System’s time and timezone are automatically synced.
No other Navigraph product is having these same issues.
After resetting Simlink (removing Navigraph folder from %AppData%, after backing it up), functionality has returned.
Spoke too soon 
Restarted my PC, and it was signed out. I signed in again for it to immediately sign out.
If removed Navigraph folder from %AppData%, it works again. Not a stable fix.
I deleted Sim Link 3 times… In third attempt I change the browser to firefox… Once it was signed out by itself,but then nothing more… Now is ok a few days…If it happens again I will do as you said… Previously I was using Opera browser…
I have encountering the same issue and it have become worse lately, it is very irritating, I have reinstall Simlink several times, delete Navigraph folder and sync time but the problem still resist.
My internet connection is stable and I have no problems with other programs that depends on stable internet connection
I logged out of Navigraph and logged in with my Google account instead, that seems to have solved the problem so far.