Cannot restore from time machine after downgrading from Mojave to High Sierra

Hello. This is my first post so I may not have posted to the correct place.

I have an iMac late 2013 model, Intel i5, 8gb ram

I have successfully downgraded from Mojave to High Sierra 10.14.6. My problem is that I cannot restore specific files from my time machine backup (which was backing up on the previous Mojave OS) to the new operating system (High Sierra). I enter time machine and the 'restore' button is greyed out.

Secondly, I tried to restore time machine through the recovery mode command + r on startup and it also would not allow me to restore. Have I lost all my data or is there a way for it to work on High Sierra?