Lucky enough to win the ballot and offered the chance to buy tickets, the deadline is tomorrow but payments are failing 
Money is taken and then refunded almost instantly.
Can you try a different card? Might help work out if its a Monzo problem, or a problem with the ticketing website.
I would try a different card even open a revokut account or something to get an instant card
Note Wimbledon are very strict do not pay with someone else’s card not in your name they can and will probably cancel your tickets as a result.
Yeah, Halifax to the rescue. First time Monzo has failed me in 9 years, so can’t complain too much.
This is just merchant acceptance.
Weirdly, I have never had a problem when buying in the resale got Wimbledon tickets for a few years without issue on Monzo
is it an address verification thing? I recently moved and had some transactions fail on a website because I’d forgotten to update my billing address.
Can’t be address as the ballot is per household. The address used is the same as my Monzo account.