Problem Loading Mail on iPhone 7+

Problem Loading Mail on iPhone 7+

For the last few weeks, for some unknown reason, Zoho mail prompts me to login to my mail account on my iPhone. It always happens at an inconvenient moment when I need to get into my mail.

After login, I get an infinite spin and the prompt at the bottom of the screen "Loading your Mailbox" (see attached screenshot). It continues forever and never loads. I'm always having to turn off my phone and turn it back on to get past the issue. After doing this, I get right into my email.

No clue as to what has changed but is there any way to fix this and prevent it from happening? Thank you.