Does anyone know if the card will still work if you have blocked yourself out of your Monzo app?
In what way are you blocked? If Monzo have closed your account then no. If you’ve just forgotten your login email then yes.
Just keep in mind that you may have issues if you try to pay online and it wants enhanced security (MasterCard 3DS) because it send a notification to your app which you have to click.
Although if you look on the payment screen it usually gives you an option to request an SMS code instead.