Hmmm, not much additional help there…!
If this was a non-TLS connection, I’d say to try to run Wireshark and snoop the req/response. Don’t think that’s possible if TLS.
Does Azure Hubs have a “connector testing” test utility or something that might provide more verbose logs on that side? I’m assuming the error you’re seeing on Solace side is all it’s getting back from Azure.