MongoS clients not seeing databases after config server change to CSRS The three config servers were migrated to CSRS and WiredTiger last week. Followed the documentation here : https://docs.mongodb.com/manual/tutorial/upgrade-config-servers-to-replica-set/

Since the change, when connected to a mongoS, we cannot see the databases after using show dbs and we cannot connect using --authenticationDatabase admin --username root --password xxxxx --authenticationMechanism SCRAM-SHA-1

There are no errors in any logs, neither mongos, on the config servers, on the mongod machines. rs.conf and rs.status are OK.
The mongos have been stopped and restarted a few times to try and rectify this, with no luck.
There were no errors during the migration process. BUT a NEW dbpath was used so the initial config server didn't use the existing details but in fact created 'empty' details in the new dbpath.

Basically when doing the migration, the first cfg server does not change it's dbpath nor it's port throughout the migration procedure. Personally I found this unclear in the procedure, especialy when you are migration from SCCC to CSRS and using WiredTiger.