The client I added the file to is running 2020 R1.2. The server is 2022 Q1. I will try updating the client.
In the meantime, I added the myAssets.json file to a different client that is running 2022 Q1 Patch 2 but again didn't see a change on the server.
Just to close on this a bit more I should say that client and server logs were a horror show of error messages. I have a lot to digest there. However, the file I added to the second machine that had a version of client SW you suggested did finally show up. I suspect the turnaround time is very much a reflection of all the errors. I'll be sorting that out separately now. Thanks again!