I’ve tried twice recently, both in different stores in London. I get declined - my location doesn’t match the merchants, apparently.
I had something similar when i tried to pay for lunch while visiting The Hague. The problem turned out to be my phone had an incorrect location being reported, so it didn’t match the location of the shop.
Making sure that the Revolut app had access to ‘fine’ location reporting (on Android) fixed the problem.
Disabling geolocation in the app should solve the problem. Usually it’s works fine, but occasionally goes haywire and says that my location doesn’t match merchant’s which is bollocks, so I keep it off most of the time.