This happens when you do not have the sender in your contacts. This is a security feature of iOS. Apple disables links from unknown contacts.

To fix this, add the sender to your contacts, if you know them, then view the invite message again

Sometimes, when you attempt to share your screen and the "Start Broadcast" button does not begin counting down, it may be due to a permissions issue where use of Screen Recording has been disabled on your device.

Follow steps below to fix:

1. Navigate to Settings → Screen Time → Content & Privacy Restrictions → Content Restrictions
2. Scroll to setting Screen Recording
3. Choose Allow

This is a security feature of iOS.

When you want to guarantee your friend is not making mistakes with password entry, have them say what they are typing letter by letter.