I can confirm that connecting via bluetooth from Mohave 10.14 to my brand new H9 does not appear to work. The H9 shows up in the bluetooth preferences as a new device (With the correct serial number). Cliking on 'connect' results in long wait followed by a 'Could not connect to this device error'
It can also be helpful to restart your H9 with the HotKnob pressed (the switch in the upper left hand corner of the H9). That will clear its system settings which can help with some Bluetooth connectivity issues.
The H9 Control manual has some trouble shooting tips in its connectivity section at the beginning of the manual:
Let us know if you continue to have problems. Unfortunately, we are limited in what we can do about these problems. Apple implements the Bluetooth connectivity layer on macOS, and the H9 is using a Bluetooth chip recommended by Apple. So, when there are problems with connectivity that cannot be solved by the standard trouble shooting tips, we ask users to capture a Bluetooth diagnostic log so we can submit it in a bug report to Apple.