Web3 wallets can sometimes be finicky and run into issues when trying to connect with mobile apps. The most common solution is to fully close/quit your MetaMask app and refresh coindesk.com before trying to connect again.
If you still have issues, try accessing coindesk.com from the MetaMask app. You can find the browser by tapping the stacked, blue lines in the top left hand corner. The “Browser” option is listed first after two pill-shaped buttons labeled “Send” and “Add Funds.” If this is your first time using your browser, you’ll be able to navigate to account.coindesk.com using the search bar on the MetaMask home page that automatically loads when used for the first time. If there’s already a loaded page, you can tap the white URL title in the middle of the navigation bar on the top of the screen.
If neither of these solutions work, you may need to use a desktop when connecting your wallet or transferring your balance. To do this, you can either create a new wallet or import your mobile wallet using the browser extension.