There seems to be a problem removing the .htaccess-Rules the plugin installed to intercept image requests.
You can try removing /wp-content/uploads/.htaccess on the server file system, this should fix it.
Thanks for the fast reply! Funny thing now is, that after activating and deactivating it a few times, all photos are there again even with deactivated plugin.
If the file is not deleted and the plugin is deleted, uploading new pictures might cause those pictures not to be displayed. So I’d suggest to either remove the file manually or leave the plugin avtive (but set watermarks to disabled on default) so that it will pick up new files correctly and flag them for the server to just serve. It should not cause any performance impact.
I’ll look into the problem and test why this file was not deleted upon plugin deactivation.
Some photos were ok and some were missing, now after deleting the htaccess file everything is ok, thank you.
The plugin seems to have had a problem with the deactivation hooks (not fireing in some configs). Now it should be fixed – so if anyone else has the problem: Update to current version first, activate plugin, then deactivate the plugin again and/or uninstall.