Help? Newbie

Hello there, apologies in advance for my cluelessness. Trying to get xmr onto my Monerujo Android app wallet, using changenow.io (new to all of this/never even used Bitcoin before) So I am trying to purchase Bitcoin so I can exchange for xmr and have sent to my Monero wallet from changenow but can't figure it out. I have like 4k on my debit card and have tried repeatedly entering it to changenow when trying (I think what I should be doing?) To buy bit from usd? But it keeps saying declined. Does a Venmo debit card/Venmo account not allow purchases at changenow?

Any and all help greatly appreciated in advance! :)