Heya! That's pretty weird. Honestly, I'm not entirely sure why your friend would be able to message you, but you can't message them back.
However, I've got a theory on what might be happening. If you're getting an error message that says something about them not having a Meta Horizon profile yet, then it sounds like they may not have migrated their Oculus account to a Meta account. If you're on a Meta account and they are still just on their Oculus account, I think it's possible that could be causing this to happen.
So you should check with your friend to see if they were able to set up their Meta account. If they haven't, let's see if they can do that first and then try messaging them again.
Let me know how that goes and if it works! If not, could you send a screenshot of the error you see? I'd like to dig into this a bit further.
Were you able to check that your friend set up their Meta account?
Are you trying to message them over chat in VR, or over Messenger? If they chose to no longer have their Facebook connected to their Meta account when setting it up, and you're trying to use Messenger, that could be a reason this is happening as well. You should then be able to use the cheat feature instead!
Also, are they able to receive messages from any other friends? If not, then it might be something on their end that isn't working right. If that's the case, then you should have them reach out to support: https://metaque.st/Support
And lastly, if it's still happening from your account after trying and checking all that stuff, you should submit a support ticket yourself so the Support Team can look into this further: https://metaque.st/Support