Try the following troubleshooting steps:

• Update to the latest version of iOS or watchOS.
• Confirm that you have Face ID, Touch ID, or a passcode set on your device.
• Check that your Apple Account is signed into iCloud with two-factor authentication turned on.
• Check whether Apple T&C’s were accepted in your settings when logging into iCloud.

If you’re still unable to add your room key contact The Guesthouse at +31 182 231254 or hello@guesthouse.nl.