I made a form and moved it to a SharePoint (group forms).
I cannot move the form back to my forms, nor to any other SharePoint.
It appears the SharePoint I moved the form to had been archived.
Even after unarchiving the SharePoint, I could not move the form back to its original place.
Thanks for your help.
I've created a 'share as template' link and pasted it in the browser. The form is then added to my forms again. Still a mystery why I would be able to access archived SharePoints through Forms and not anywhere else.