Hi Ernst,

1. Update Helix plugin
2. Watch that video: https://youtu.be/ZO9nmdsLlFw

then

share error screen if you cannot solve it

By the way: the module that produces the errors seems to have something to do with acy-mailing. Here is a part of the last error message:

#   Function    Location
1   ()  JROOT/plugins/system/regacymailing/regacymailing.php:705
2   plgSystemRegacymailing->_addCSS()   JROOT/plugins/system/regacymailing/regacymailing.php:233
3   plgSystemRegacymailing->onAfterRender() JROOT/libraries/src/Plugin/CMSPlugin.php:279
4   Joomla\CMS\Plugin\CMSPlugin->Joomla\CMS\Plugin\{closure}()  JROOT/libraries/vendor/joomla/event/src/Dispatcher.php:486

As I said, I can't see any further through this :-(

Thanks, indeed, old acymailing plugin made that mess.

Solution:

1. Detele that folder: plugins/system/regacymailing
2. Uninstall Acymaling from Joomla (component, modules, all plugins,) and if you want to use newsletter: download & install new version (v8, not v5x as it was).
3. That's all.

Hi Paul

Thank you very much for the support.

Apparently I didn't save my first response to your original reply, so here are some notes on that one again:

The video was very helpful and I have enabled debugging as described. I then saw that the problem was with the acymaling plugin.

The video also recommends replacing the isAdmin() method with isClient('admin'). In another forum I saw the same recommendation, but there isClient('administrator') is used. Is this equivalent or does only one of the two methods work?

And regarding Aycmailing plugin: will try according to your instructions.

Many greetings Ernst

In your case - problem is/was with old plugin(s), so changing code doesn't make sense if there is a new version already and free.

Hi Paul,

your advice works!

Regards Ernst