Question ERR [1] Token validation failed: ; ;

[FireHost1]

After some trouble with an Plesk-Upgrade on Onyx 17.8.11, we cannot open Extensions or WordPress Toolkit. I enabled the Debug Mode ans saw multiple errors in panel.log:

[2020-02-15 13:24:02.576] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:03.098] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:03.354] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:03.547] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:03.727] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:03.877] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:04.898] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:05.088] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:05.315] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:05.540] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:05.888] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:06.427] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:07.988] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:08.105] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:09.078] ERR [1] Token validation failed: ; ;
[2020-02-15 13:24:10.392] ERR [1] Token validation failed: ; ;

How can i solve this???