Is there a way to restore the default form on a sharepoint list using a customised list?

[Victoria Symons]

I have published a PowerApps customised form to a SharePoint list believing I could switch back the list back to the default form. I should be able to do this. However in list settings > form settings, the settings are missing. I have 'The list does not have any valid content type' instead. 

This is problematic because this list is live and the PowerApp is nowhere near finished yet. I could really do with switching it back. Does anyone know how to restore a default list form in SharePoint or how it might have got deleted? It was there before I created the PowerApp. I have not intentionally deleted it. Thanks so much. 

[#2]

Tray to grab the URL that allow to change the list form setting from another list and see if you can change the setting in the customized list

[#3]

I have the same issue. Most posts related to similar problems that I found on the web refer to the list settings which I do not have access from the List Web Application. Very frustrating. I feel like an Apple user using an Android application. Sigh!

[#4]

@JPhReid 
I'm sorry to say I never managed to resolve it. I just had to work quickly. The only thing that occurred to me was that my list was on a classic site, all be it, in the modern view. Spoke to Microsoft at the time and they didn't know why it had happened or a way to get my old form back. 

[#5]

If you go into the All Files Section of SharePoint Designer you can copy a working default form from a library that works and then adjust the GUID in that form, while most things in SharePoint Designer are deprecated this work around still seems to work at least at the moment.

[#6]

For anyone that has the problem, go to list settings--->Form settings ---> and select "Use the default SharePoint form"