This is a weird one that just started happening and I am at a complete loss. I create a new custom form element block in code but it is not being picked up by the UI. It's not in the Form Elements gadget and it is not listed when you click "create a new form element".
The View is in the right location.
Now when you go under Admin > Content Type > Block Types you can see the info and everything looks fine.
Even if I make a copy of an existing element (add a 2 to the name, generate a new GUID) that copy won't show up either.
Can you try to move your element to fresh Alloy site to see if it shown. One reason that you could consider is caching of ASP.NET. Try to clear the folder C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files (correct your path) and refresh the site.
Yeah, I replaced my local database with a backup from Integration and the problem went away. Super weird.