I wish that I had found this post sooner! I have spent at least 10 hours looking into this issue (Claude had me looking into a lot of empty rabbit holes). I too am trying to communicate with a Mini-Circuits ZTM RF switch. A former co-worker wrote the driver for this instrument and it has been used for at least 6 years on 20+ PC's across multiple labview versions beginning with 2017 and now 2026 without issue. Before finding this post I too was able get those commands to work using the double ??.
This post is good confirmation that its not just my setup. I don't see a way to downgrade just NI-Curl so I guess i will need to update this driver to comply. Fortunately the double ?? also works with the older labview versions.
