I'm new to redundancy, but I set up the Master and Backup per the documentation and it appears to be correct. I'm using cold start because I have 9k tags on one PLC (most rarely updating or disabled, but still...). I have one Perspective Workstation connected.
When all is running normally, the Master says Active, the Backup says Cold, and they both say Synchronization: Good.
When I go to the Backup and click "Request Failover", my Perspective session says disconnected for a moment, then automatically reloads the project and the Backup is now serving the project. The Perspective session is visible in the "Perspective Sessions" tab of the Backup's Status page. All is good.
Then I "Assume Control" with the Master, the Perspective station reloads, and everything is back to normal. All still good.
Now I go to the VM hosting the Master, and I go to services and stop the Ignition gateway service. The Perspective Workstation loses connection, then ... just stays like that. Meanwhile, logging into the backup gateway, it now says "Activity Level: Active" and it's communicating with my OPC device. But Workstation does not redirect. And the session is not visible under "Perspective Sessions" on the Backup.
What am I missing? Why doesn't the Workstation switch to the Backup?
The community is pretty quick to respond, so I'm guessing that the few days of silence means it sounds like I'm generally following the expected procedure.
Any pointers on the next places to look as I'm trying to troubleshoot this? Would there be any telltale activity hidden in one of the logs where some sort of message should be broadcast to active client sessions by the backup server telling them to reload and repoint, and maybe that's erroring out or getting bypassed?
I would suggest that you get in contact with support on Monday morning.
Lol, fair enough. My production floor has a whole host of non-edge ignition gateways acting as Edge devices, and I can't afford support agreement on all of them, especially when they're all almost identical - so I just pay one big support agreement fee on our biggest license. Unfortunately we're trying out the redundancy feature and it's on one of the other gateways that doesn't have support, so it will be an expensive tech support call to buy the contract for the one call.
I do want Inductive to make money though - they make amazing stuff. I just don't always have it to give 
If you are trying it out, and if it works successfully then you will purchase the license, then you should get the help you need.
{Perhaps ask for sales engineering, not technical support}
Did you receive any resolution on this issue? I am having the same issue myself.