I am configuring a mongodb replica set. From my current primary node, when rs.add('host1:27017'), it yields this error
Quorum check failed because not enough voting nodes responded; required 2 but only the following 1 voting nodes responded; the following nodes did not respond affirmatively; failed with Server min and max wire version are incompatible (7,7) with client min wire version (6,6)
On my host1 and host2 machines, I already added replication option with the same replSetName, bind_ip, and exposed firewall. As a proof, through command line mongo --host host1 I can still connect to host1's mongo instance. The telnet command also yields the same successful connection. I don't know how to fix this.
The answer is that all 3 machines must have the same version 4.0