Invalid form token even when logging in

Translation from google:
When trying to login to the site
https://www.polna.org/fundacja/index.php/login
message appears:
Invalid form token. Please reload this form and submit again.

I have installed concrete5 9.1.3 with PHP 8.1 on the server.

For a few days I tried to set up a website and usually after an hour of setting up the above message popped up. Mostly after setting the canonical URL, but now it’s at login.
After uninstalling and reinstalling concrete5, I manage to set something up for several dozen minutes, but my website creation usually ends with the above message.
How do I create a page?

Could the login page be cached? Does your host have any static cache fronting the web server?

I wrote this question to hosting and they wrote back this (Translation from google):
“We do not cache anything by default on our part, but if you enabled LS Cache or Redis, it is unlikely in our opinion, although it is possible that this is causing the problem.”
I didn’t turn on anything.

Check cpanel to be sure there is no caching enabled. My server always has this turned on by default for new domains, and would cause me headaches. Now I know to go turn it off every time!!

Thank you, it clearly helped - I was running for 5 hours. However, after setting Canonical URLs, the token showed up.
Now after reinstalling in logged in mode it works, but the page after adding an additional language stopped opening.
error 403
Access to this resource on the server is denied!

I’ll practice some more and thanks again for your help.