MainWP Plugin dissapears when activating

Hello,

When i activate the plugin, the plugin dissapears. It wont show up in the plugin list and also i dont see him at settings > mainwp.
I tried all kind of things.
– Deactivated all plugins > same result
– Uploaded mainwp child plugin instead of install from WP plugin database > same result
– Extracted zip in plugin directory trought FTP > same result
The strange thing is that the plugin is visible in FTP plugins list at wp-content. And also the big red alert is showing up: Attention! Please add this site to your MainWP Dashboard NOW or deactivate the MainWP….

But when i want to add to plugin into my mainwp, then the plugin cant be found.
Any idea what i can try now?

Thanks ??