Time Machine not seeing my external backup drive

The external (1TB) WD drive that I use as my Time Machine Backup filled up and stopped backing up.

Rightly or wrongly, I saved the most recent backup file to another external drive and then via Disk Utility repaired then erased all.
I then transferred the most recent backup onto the erased (1TB) drive.
But the Time Machine is not seeing it anymore so I can’t “select” it? It shows in Finder etc.

I have spent hours and hours trying various online fixes – namely, in “sharing” checking the AFP option along with the SMB but nothing seems to work? Any advice very gratefully received.