I have been creating a form on SharePoint 2019 with no problems, but when i went to save the form, it closed and went to the list, upon re-opening it asked if i wanted to create a responsive or use classic view as if there wasn't a form there.  After refreshing the page, the form came back, but now i don't have the menu options on the left hand side, i've tried re-sizing my Edge window (zooming out), but they do not appear.  I've cleared my cache and re-opened Edge, but it's still not showing up.

Has anyone else experienced this and has resolved it?

UPDATE: I have now noticed that none of the controls on the form can be moved and I cannot drag any new controls from the visible left menu onto the form