Blackberry Mail App - Cant See Emails

Blackberry Mail App - Cant See Emails

I have the Zoho Mail App for Blackberry from the Amazon store installed on my Blackberry Leap (latest Blackberry OS installed).  Everything was working great on it at first.  I was able to send and review received emails without issue, use the calendar and so on.  But all of a sudden I can no longer see any emails in any of my folders on the app.  I can send emails without any issue, but none of the emails in my inbox or any other folder appear on the application.  

I have tried logging out and logging in, as well as uninstalling and reinstalling the app, but have had no success.  

Is there a fix for this?