Exchange Hybrid GAL

We have the following situation.

A few company/forest share the same tenant with the AADC configured in the Main Corporate network.

Each company has his own windows domain/forest with exchange on-prem that is being migrated to O365.

After migrating a user from one company's on-prem exchange to O365 it does not show up in the GAL and the automapping is not working anymore, though email flow is working just fine.

Has anyone had the same issues ?

The Exchange on-prem is Exchange 2010 with an exchange 2016 "hybrid" server.

thanks