I just tested the whole setup in 1.4.4, and it works well. So something you may take a look.
After Step 4, take a look if RAFT runs correctly. You can take a look on the log of five orderers.
docker logs orderer.example.com
See if you can capture this for channel
testchainid (the default name for system channel as I didn’t change it).
That’s what I see in mine.
2020-04-22 00:10:24.907 UTC [orderer.consensus.etcdraft] run -> INFO 03c raft.node: 1 elected leader 1 at term 2 channel=testchainid node=1
2020-04-22 00:10:24.950 UTC [orderer.consensus.etcdraft] run -> INFO 028 raft.node: 2 elected leader 1 at term 2 channel=testchainid node=2
similar can be found in orderer3, 4 and 5.
If you can’t see it, the RAFT is not successfully established.
When you say using SOLO, are you also deploying it across Docker Swarm? If so communication between hosts should work well. Still can’t figure out the root cause in your case.