I too have had long-standing issues with the H9-to-MBP bluetooth connection, whereas the H9-to-iPad bluetooth connection is quite reliable.  I was eventually able to get my H9s to connect to my MBP after troubleshooting both devices, and ever since I’ve had decent success connecting to one H9 at a time via MBP.  But I’ve NEVER been able to get the MBP to connect to my two H9s at the same time via bluetooth.  Whenever I add a second one, the previously-connected one gets booted.

Any ideas?  Any more effort to remedy this?  This “one at a time” limitation for bluetooth on MBP has persisted for well over a year…