First of all, as @c0stin already said but just to be sure, I’d go to “Card Security” in the app and make sure everything there is disabled (also “Location-based security”). Then, I’d also make sure there is no limit set for your card.
Is there any record of the failed transactions in the app? Note that this would appear under your main currency (GBP if you were UK-based at the time of creating your account or EUR otherwise), even if your balance is all in USD.
Have you tried another ATM? Some ATMs never seem to work with Revolut, although it’s rare. Also, some classes of merchants (petrol stations) are entirely banned. In the latter situation, there would be a message saying “Merchant is not supported” for the attempted transaction.
In some countries (Japan), most ATMs only accept local cards, although they confusingly have Visa/MC logos on them. Could this be your situation?
In a shop if the contactless payment doesn’t go through you can ask them to try again with the chip, or vice versa.