If you have Error 1005 with the wording 'The Microsoft Exchange RPC service can't be started because the EMSMDB interface is already registered by another process' within your event log and the 'Microsoft Exchange RPC Client Access' service will not start this may resolve your issue.
- Stop all Services to do with Microsoft Exchange using the topology Service
- Make sure they are all stopped as some may restart right away
- Once confirmed they are all stopped you will need to start the RPC client access service firstly making sure it is 'Started' before starting the other services one by one
If this does not work stop any other RPC services within Services and start the process again.