Black screen on filevault prebooter after installing filevault

Hi all,

I got my Mojave hackintosh running over the weekend. Today I decided to add filevault. I followed the instructions at https://davejansen.com/turning-on-filevault-on-your-hackintosh/

After completing the encryption, I rebooted and selected the filevault preboot option in clover. This just takes me to a black screen, and no amount of waiting changes that.

My spec is

• Gigabyte Z370 DS3H motherboard
• Intel CORE I5-9600K
• 16GB RAM
• Samsung 970 m.2 nvme drive
• Gigabyte vega 64 GPU

I'm not emotional about any of the content as I have full backups - not quite ready to move to it full time yet. But any ideas on what I might have done wrong? I can't work out what the differences between the guide I followed and the instructions at https://www.reddit.com/r/hackintosh/comments/cre5da/filevault_howto/ are.