As someone who’s a complete beginner to crypto, can someone please help me make this Monero payment for Mullvad VPN?

HI. Hope you’re doing well. Been looking at various VPN options and all the pros and cons and decided on Mullvad. However, I want to pick the safest payment options that cannot be traced back to me and heard Monero is among the best ones. But as a complete beginner to crypto, I downloaded the Monero.com app on iOS and I went on Mullvad‘s website and got the account number and one-time payment address and went to the pay with Monero page and clicked the “Open in wallet” button that took me directly to the Monero.com app, but all I get in the app when pressing the “continue” button is a “Transaction Error. No inputs provided, transaction cannot be constructed.” Can someone please help? I could just go with ExpressVPN or NordVPN instead for simplicity, but I want to go the extra mile by going for the most privacy-friendly VPN with an anonymous payment method and Mullvad seems like a great choice, but only if I can pay anonymously. I know I could pay with cash, but it’d take longer and more of a hassle.