I'm running an iPad Pro with Touch ID, iOS 13.3, v5.85 of the H9 firmware (on two H9 pedals) and the latest version of H9 Control. I have tried importing from within the H9 Control app, and also by tapping the presets in the Files app, and setting them to be opened by H9 Control. Neither works. I am able to import presets into the Mac version of H9 Control, but it's much more cumbersome to plug the pedal in with a USB cable to sync them. I ended up loading a bunch of presets to a new Preset List on the Mac, syncing them all to one of my pedals, amd then syncing from the pedal to the iPad. I'd love to just do this via Bluetooth.
On iOS devices, you need to put preset files into the H9 Control folder in the Files app. Here is a demo video of how to do that: https://share.eventide.com/wl/?id=NEnU6hfPVDBTjCCJwuEUIAdHBvlPIhp4
BTW, you can also connect to your H9 on your Mac via Bluetooth. You can do so by clicking "Manually select a device -> Connect via Bluetooth -> now select your H9 and click Browse"