Zoho mail app crashing on open - iPad pro

Zoho mail app crashing on open - iPad pro

After months of use suddenly this morning the mail app (latest version) is crashing when I try to open it rendering it useless.
I have uninstalled and reinstalled the app. I have rebooted the iPad. The iPad OS is 11.0.2.

When the home button is double clicked showing all open apps, the email app is there, swipe up it “closes” but it never opens for use.