After new user added to MIAB can't login with mobile

I created a new user with a new domain. Pointed DNS and all the above but when ios device connects via excahnge active sync it keep prompting to re enter the password even after the device got all the checks passed. I did this intially on the default domain I created and then after a reinstall of MIAB it works. Now adding another domain and email box it won’t log in with correct credentials.

Can anyone help?