At MID server folder (<MID_server_installation_path>/work/mibs), no mibs files being synchronize from instance.
Some of the MIB file at instance side have 0kb causing the instance unable to sync the file to MID server.
Check all MIBs file in instance and ensure all attachments in records are valid.
You can also check mid server agent log to get an idea on where the synchronization failed. In following example, the mibs record "FOUNDRY-SN-ROOT-MIB" in table "ecc_agent_mib" is causing the synchronisation issue as the attachment in the record is having 0Kb.