Designer changes don't show up

I have tested one of my form in form designer and I was able to save changes.

I would suggest you to first clear your browser cache and form's cache, log back in and see it fixes the problem. Also may I know if what web browser you are using, and if you have tested it on different ones? If after that you are still unable to save changes and see it on preview, please let us know which forms you are having problems with.

Hope this will help.