Could you please post the output of fastboot oem device-info 
What is the current state of your phone, does it boot into Android userland, are you getting any bootloops.
Did the installation go through or did it fail with an error? 
If you can successfully run an installation my advice would be to modifiy the install script as outlined here:
Don’t boot into Android userland at that point, we want to stay in the bootloader!
Unless the partition that stores get_unlock_ability is part of the critical partitions (which I don’t think it is) that should reset that value to 1 and you should be able to issue fastboot flashing unlock_critical 
Edit: Yeah, nope, scratch that, I checked the install script and it won’t let us go through with it, and we are not going down the manual route. This calls for the Magisk method.
You’ll need the latest Magisk app and the boot.img that you can find in the images folder where you extracted the factory images to (not the old ones, we want the images matching your current install). Transfer both to your phone, install the app, go to Install → Select and patch file, patch the boot.img and transfer it back to your PC. (I can do that part for you if you are struggling, but I don’t have time right now)
Then it’s basically:
after that you should be able to use fastboot flashing unlock_critical