I have a custom editform.aspx page that has a number of items suited to my use case. After our migration, all forms are working fine. However, I needed to make a change to my custom form, and as soon as I make the smallest of changes (just putting an alert into my js for instance), all html disappears from the page:
The html is present in the form in SPD, but when I inspect the source, all html is gone. All I can see in the form are the Save and Close buttons. I've been scouring the internet but cannot find a fix. What can I do?
for the test purpose try to delete migrated form and customize again. Looks like form parsing would be an issue, if you have access to IIS logs in server this would be the place to look for an issue. for now, try: List Settings > Form Settings under General Settings > Select User the default SharePoint form and delete the InfoPath Form from the server > Click OK.
And check if you can customize form and how it behaves.