Unable to search internal email contacts in Teams

[Damilare1]

There are two domains (A&B) in my office 365 tenant. when a user in domain A logs into Teams, that user can search for users in domain B but if a user in domain B logs into teams that user can not search for users in domain A. Also, they are unable to add them as contacts in Teams for calls. It return error "we didn't find any matches". Please can anyone help on this?

[#2]

@Damilare1 By domain do you mean AD domains? How is Azure AD Connect set up? Single tenant ?What happens in exchange online?

[#3]

Yes single office 365 tenant but two domains (.onmicrosoft.com and one other domain) both in a single office 365 tenant. Both use exchange online