Problem with update

I just installed the newest update now and my forms won’t show up.
Bottom left corner has a message “Creating index.html”

How are you running your app?

This is what it looks like.

I uninstalled and then installed the previous version. Same results.
So it appears that this is not related to the update.
Any ideas from the support team on a fix?

The last thing I did before this happened was to add a .png background image to a form.
I just removed that image from the form’s properties, but still, no forms show.

I had added background images to 2 forms. I just removed those and it all works.
I’d be happy for someone to tell me how I can add a background image and have this not happen.