Summary:
I used Mockup yesterday on my iPad (iPadOS 14.3) and it worked great like always. Today I was going to export my sketches, but the app will not open. When tapping the Mockup icon, white screen pops up and then it crashes. I downloaded an update from AppStore but the same problem persists. I tried installing the app again. My internet connection is also working fine and all the other apps on iPad are working. I really need my sketches urgently so this is very unfortunate 
Mockup version: 2.4
Device type: iPad
OS version: iPadOS 14.3