I have a three 2010 event handlers installed on-premises on 2013 foundation that are all part of the same solution (added, updating, updated), none of which are triggering when they are attached to the list (confirmed by SP Manager). I've tried writing to a list at the start of the code to show that it's running but failed. Additionally, I created a new 2010 solution that successfully writes to a list. The solution has been retracted and reactivated but still no luck. What could be the possible confliction(s) for these not running?
Make sure that the event receivers exist in one of your project features. also make sure that this feature is activated on your website. Finally try to change the scope of the feature (I don't think it will work if the scope is "Web", try to make it "Site") P.S. You don't have to add code for testing writing to a list to show that it's running. You can just attach debugger to your IIS Worker Process (w3wp) and insert break point at the start of your code.