Password not accepted (reinstalled PC) free version

Hi, I am trying to connect to a PC wich has Teamviewer free version installed,
but it keeps rejecting the password even tough the password is correct,
I have created new random passwords, but it does not help, and it is not a typo error.
I can connect to the machine if I add it to my teamviewer-account with a manually entered password btw.

I have tried to restart the teamviewer-service, but no go
I have tried to uninstall and reinstall teamviewer, but no go

This machine have had teamviewer installed earlier on, but we have reinstalled
windows 10 on it.

What to do?