When you get an error like this: Notice: Trying to get property ‘id’ of non-object in class-fs-plugin-manager.php, it means that you probably migrated the data from one site to another and the data got corrupted along the way. The fastest solution is the following:
1- Go to “yoursite.com/wp-admin/admin.php?page=freemius
2- If the page loads properly, you should be able to see the list of plugins that use freemius
3- If our plugin is there, click “delete all accounts”
4- Click “clear API cache”
5- Click “sync data from server”
6- Go to the list of plugins on your site, look for our plugin and click “activate”
7- Also, clearing all the server caches and object cache might help
8- If you use object cache and the steps above didn’t help, try deactivating the object cache temporarily
