Error 503 Backend fetch failed

I can’t access to my matomo server installation anymore.
I get this error:

Error 503 Backend fetch failed

Backend fetch failed
Guru Meditation:

XID: 54112105

Varnish cache server

What should I do now?

Hi @Ksasa
Check the error log file

Hi Philippe, do you mean matomo.log? I don’t have this file in /tmp/logs/
Or I have to check in some other locations?

Have a look at:

Ok thanks, it started loggin in there:

ERROR Piwik\ExceptionHandler[2022-10-28 09:37:42 UTC] [1a26a] Uncaught exception: /my_matomo_path/matomo/core/Nonce.php(236): Non è possibile verificare il token di sicurezza di questo form. [Query: ?module=CoreUpdater&action=oneClickUpdate&nonce=ecd4ac49923d91c7b061eb4699777884, CLI mode: 0]

the error is written in Italian, the english translation is:
It is not possible to verify the security token of this form

The system writes 3 lines of this error at every access attempt.
it’s the only kind of error shown in the log.


Try to remove any stored data in your browser or navigate in Private mode. Probably some cookie has not been deleted…

so… it turns out that this only happens trying to access at index.php?module=CoreUpdater&action=newVersionAvailable
when there is not a new available version. When entering from index.php all works fine.
Still seems strange to me that entering in the CoreUpdater returns that 503 error. I have also tried entering from another browser, never used before for that matomo installation and there’s the same problem.