Open up the latest log file in the directory and see what errors are being reported by the client.
In our case, we had these error messages: Notice the error “Is Local OABFile Current: Manifest Enforcement Disabled And Local File Too Old”.
If the update mechanism appears to be broken for you, it could be because of a corruption in your OAB or in your mail profile.
Learn how offline address books are created and distributed in Exchange 2016.
An offline address book (OAB) is a local copy of an address list collection.
This copy provides quick access to your data, and it is frequently updated with the server that runs Microsoft Exchange.
If you want to turn off Cached Exchange Mode, repeat the steps, but clear Use Cached Exchange Mode.(This could take several minutes) Step 2: Uncheck the box next to Download changes since last Send/Receive.
You can configure which address lists are included in an OAB, access to specific OABs, how frequently the OABs are generated, and where the OABs are distributed from.