By skyforbes 
for some who didn't find a way, i found one!
you can probably do this also on your mobile but i did it my on laptop.
first is go to google wallet, make sure that the wallet that is linked in there has a balance. for our currency it took my 10 PESOS but will return it in a minute.
– if there's no wallet, link a wallet with balance in it so google can proceed.
if you have successfully linked your wallet with enough balance. go to the email and click that "Get Google AI Pro" then follow all the prompts, it should be processed as the problem here before is the wallet that was linked.
how did i know? on mobile, it does not show me the error why, however when i tried it on laptop, it asked me the probabilities which is about the wallet (expired or no balance.)
that's it, enjoy your 1yr google pro! (offer expires on 9th on dec. 2025, go get it now)