Enable Notifications Button Not Working

Hello,
I noticed that I stopped receiving notifications from the Zoho app on my iPhone. I double checked that notifications were still turned on in my phone settings, and they were. I went into the Zoho Mail app settings, and the Enable Notifications button is now turned off. When I try to turn the button back on, it moves back to the off position and I get the message "Darn! Please try again later". I tried this on the Zoho Mail app on my iPad and had the same result. The Enable Notifications button is off and won't let me turn it back on.

I did delete and then reinstall the Zoho Mail app on my phone, but am still having the same issue. Any help would be appreciated - thanks!