We have migrated our SharePoint 2010 web app to SharePoint 2013 server in compatibility mode. This was working fine for few months. Now we did the upgrade of the site collection to 2013 mode by running through the UI wizard. This operation completed successfully.
- ribbon bar items (all) grayed out for the pages navigated from the settings page. for eg. site permissions page. We switched to OOB Seattle and Oslo master pages, but with the same issue.
- Also, the dropdown menu next to doc or list items won't open. or the box that displays site collection administrators in the add site collection administrator page is missing.
- No site collection admin box.