I've tried to use both my card and paypal to pay for an app on three different devices (desktop computer, phone, and tablet). None of them work and on my phone I get "Error. We couldn't complete your request." I've tried different apps too so its not a problem with the app or the way I'm accessing the play store. I have 2-step verification turned off.
*Now it won't even show certain paid apps on my phone in the google play store. (The two apps I'm trying to purchase both don't show)
*edit2: I believe the cause may be that I'm not in the US (where I got the free version of the app I'm trying to buy) and it may not be in the UK version of google play store.