Used Monzo card in store year ago without any problems.
As I know they don’t accept credit cards except Amex
I’m so glad it wasn’t just me who had this problem! I had to resort to using our Nationwide credit card which is Visa Credit as neither mine nor my partners Monzo card worked when trying to renew online with costco.
Hmm strange, Monzo is accepted at Costco it looks like it may have been a temporary issue as stated there was a 3DS decline.
Sometimes when merchants attempt the connection for whatever reason it doesnt reach Monzo or Monzo can’t send it back.
If you reach out to us via chat or phone we can check further for you 