Chevereto configuration for running this add-on:

1. Go to Dashboard -> Settings
2. Then switch to Additional settings
3. Enable the Plugin route

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There're some known issues with the button you can read here: https://chevereto.com/community/forums/bug-tracking.45/

Especially with mobile view there is an issue 'cause the different editor toolbars in XenForo. The Chevereto PUP is looking for an entry point to set the new button, mostly it is the "Insert image"-button. If in mobile view the button doesn't exist, because you as admin disabled it, then there is no chevereto button.