Fatal Error after upgrade to v5.10.1

Support & Bugs
1

Hi Forum Users,

Around the 7th May 2026 I upgrade my Matomo installation from the previous version to v5.10.1 and got a fatal error. I am now back to trying to resolve the issue.

Note my Motomo/Piwik installation is on a shared hosting platform. Yes it was originally installed when Piwik. I do not have have permissions to run Motomo CLI commands.

The initial fatal error is:

A fatal error occurred

Please contact the system administrator, or login to Matomo to learn more.

If you are Super User, but cannot login because of this error, you can still troubleshoot further. Follow these steps:

  1. open the config/config.ini.php file and look for the salt value under [General].
  2. edit this current URL you are viewing and add the following text (replacing salt_value_from_config by the salt value from the config file):

index.php?i_am_super_user=salt_value_from_config&....

I followed the suggestion and then get the following fatal error:

A fatal error occurred

The following error just broke Matomo (v5.10.1):

variable @theme-color-border-alternative is undefined in file anonymous-file-0.less in anonymous-file-0.less
in /home/ffenestr/public_html/piwik/core/AssetManager/UIAssetMerger/StylesheetUIAssetMerger.php line 54

I have tried the trouble shooting and further trouble shooting suggestions with no joy.

I would really appreciate some guidance on how to to resolve the fatal errors.

Any suggestions will be much appreciated.

Kind regards,

Huw

1 Like