I am trying to use my card to but a train ticket, and i changed my pin at a bank machine but it wouldn’t work, and cannot get the app on my iPad. I wonder if you could send me a new card
Can you not access the help on the phone app you signed up on?
Email help@monzo.com or call the number on the back of your card, they’ll sort it for you 
Even though there isn’t an iPad app, you should be able to install the iPhone app (Monzo Bank - Mobile Banking on the App Store) on your iPad.