Cant restore U2F from 2018 onlykey backup

Hey, I have been using onlykey for years. I got my key back in 2018 possibly early 2019 and made a backup. (I do not remember the firmware version and am afraid to have the new software interface with it.)

I just purchased a new onlykey and restore my backup file. My slots work as expected and all my stored passwords work fine, however when I try to authenticate via any U2F service (google account for example) it says the key is not recognized.

I seem to remember reading in an update that went out sometime in 2019 that with the new introduction of the FIDO2 standard the U2F key was generated differently than previous firmwares and a new key pairing would need to occur even with an old backup. Can you confirm this? Is there any workaround?

That is correct, the FIDO2 protocol works differently than the old FIDO U2F. The last firmware supporting the old FIDO U2F is Beta 7, Beta 8+ uses FIDO2 which requires reregistering.