Thank you for your answer.
I am glad that the problem does not affect only me:)
I did “Deactivation and keep SSL” but the error stays.
When I did deactivation of the RSSSL plugin on the Installed Plugins list, I was logged out from the site. But when I logged in again this Issue disappeared and occured new one “Only parts of your site are using HTTPS”.
Is there anything that tells you why this is happening?
Where to look for the cause?
Does it have anything to do with the Lite Speed server?
Of course I would like to keep the RSSSL plugin as well as The mixed content fixer and .htaccess redirect activated.
Regards,
Greg