Issue Cannot login to Plesk Admin after upgrade to 17.8

[PabloN]

After a normal upgrade to 17.8 cannot login anymore to Plesk Administrator. After the upgrade, I had no problem to login. I tryed to Install Modsecutiry, and that failed. I continue to login normally. Day after, cannot login anymore. Only error from the night is:

ModSecurity is not installed on the server.

Any idea? Thanks!