The problem child service that PlayStation Stars seems to be borked in the UK at this time. Residents can’t seem to redeem points for cash off transactions.
The free-to-join service lets gamers earn rewards for playing games and also purchasing new ones with some instances providing monetary value to your next transaction. As Push Square points out, though, it seems to be running into technical difficulties or at the very least heavily nerfed for UK players who are currently unable to redeem points for dollars off their purchases.
Notably, US and other regions seem unaffected by the problem, though, it’s suspected to be tied to the recent policy barring members from using their points on PlayStation Plus subscriptions.