After the installation of RegularLabs Tabsaccordions Pro 2.1.2 we got the following error:But the file src/Params.php with namespace "RegularLabs\Plugin\System\TabsAccordions" is available in the webspace.
What could be the reason?

Also we tried to install Regular Labs Extension Manager, Error:in some provider.php (don't remember... ...)

We have in system installed and enabled:
- Joomla 5.1.1
- Regular Labs Library 24.3.3300
- Plugin System Regular Labs 24.3.3300
- System - Regular Labs - Modules Anywhere 8.1.1PRO
- System - Regular Labs - Modals 14.0.12PRO
- System - Regular Labs - Articles Anywhere 16.0.5PRO
- System - Regular Labs - Advanced Module Manager 9.9.0
- Regular Labs - Conditions 24.3.3300
- Regular Labs - Advanced Module Manager (Component) 10.0.21

Thanks for your help!

Thanks for your help! It works now.
But I had to put the following line manually into the file autoload_psr4.php:I don't know why, I tried to clear the cache, remove the file autoload_psr4.php, then even reinstall the regular labs library, the regular labs system plugin and the tabsaccordions system plugin separately.