No Login via Web possible!

Hello everyone,
I hope that after searching for hours and trying out nearly everything, I just have to ask for help.
So foremost, my package:
Running under Plesk with Ubuntu 20.04 everything was perfect until I upgraded to the Version 5.5.13!
To put it clear, the iOS, and macOS Versions run very good, I just can’t log in via Web browser.

The Problem is that somehow the Permissions went wrong, and I don’t have a clou where to change it.
I hope some one off you Guys can help me.

Here the Error log that I get:
[client] ModSecurity: Access denied with code 403 (phase 2). Match of “pmFromFile userdata_wl_extensions” against “TX:extension” required. [file “/etc/apache2/modsecurity.d/rules/comodo_free/10_HTTP_HTTP.conf”] [line “27”] [id “xxxxxx”] [rev “4”] [msg “COMODO WAF: URL file extension is restricted by policy|||F|2”] [data “”] [severity “CRITICAL”] [tag “CWAF”] [tag “HTTP”] [hostname “”] [uri “//”] [unique_id “xxxxU”], referer:

I even tried to put the ID Number from this Error into the ModSecruity so that this doesn’t Block anything, but somehow that didn’t work either.

Oh yeah, the Client page works fine too.
Just one Thoth while writing, what if I would leave this then everything works fine and so no one could hack my site, or is this a little too strange thinking.

Thanks for the help in advance, and Sorry about my English, but in Vienna/Austria you don’t talk and write that often in English.

it appears some kind of modsecurity rule issue… file extension is restricted… you’ll want to white list or disable mod sec.