Per chance do you use a case with this iPhone? If so, would it be the clear case? It was reported awhile back that this case can prevent the MagSafe Wallet from providing it location to the phone.
One thing to keep in mind: Although the MagSafe Wallet does work with Apple's Find My network, it's not trackable like a lost iPhone or AirTag. Instead, the wallet uses NFC to tell your iPhone when it's attached. When your wallet is removed from your iPhone for > one minute, you'll receive a notification letting you know your wallet is no longer attached, along with its last known location that was detected by your phone.
There were, at least, two generations of the MagSafe Wallet. The 1st gen did not support Find My. I'm assuming that yours is the 2nd gen, that does ... or, at least, it did when you first got it.