Issue with ARS 7.4.3 upgrade from 7.3.1 after breaking replication and converting Pub to standalone. Config Manager loaded and returned instance related error

We upgraded the binaries for ARS 7.3.1 to 7.4.3 on our publisher host after breaking replication and demoting the pub.

On Launch of configuration manager - seeing the new DB names to be created, and clicking NEXT we get an error about an object not being set to a reference … or some such.

Not in the troubleshooting guide - and applying the appropriate hot fixes for 7.4.3 changed nothing.