Please go to the Bluetooth menu of the H90 and choose the “Forget” option. You will be prompted to confirm the selection.

After that, go to the Bluetooth preferences of your Mac/iPad and “forget” any H90 devices you may see in the settings.

After this is done, follow the instructions from the user guide to use H90 Control for the pairing/connection process: 7.3. Bluetooth — Eventide H90 documentation  

Let me know what happens.