Android exchange stopped working

Android exchange stopped working

Although the sync says it has completed fine, my zoho contacts have disappeared from my phone and using gmail app just hangs saying "waiting for sync" when trying to get mail. Is there anything I can do to fix this? Do I need to delete the account and re-create it?

settings:
username and password: set correctly

server: msync.zoho.com
port: 443
security type: SSL/TLS

"validating server settings" completes without error.

On the zoho side: activesync is enabled, two factor authentication is disabled.