Latest software update has prevented access to contactless payments via Google wallet. Samsung appear not to be accepting that this problem exists yet it arose immediately after software update. Before that, contactless always worked perfectly well.
What phone do you have? I use the A53 with the latest update and Google wallet works fine. Have you tried clearing the cache in the app and then uninstall and reinstall it to see if he helps. I would also double check the NFC hasn't been turned off accidentally.
I've got the A52s and yes I've done everything you suggest. Wallet worked fine for a year until I did a software update at the weekend. Google have confirmed all good at their end. Samsung were very indecisive and hesitant as if they knew ow there's a problem. The promised return call to assist never materialised.