You can write your topic however you want, but you need to answer these questions:
What do you want to achieve? Keep it simple and clear!
Understand what this error message means and how to fix it:
IXP - Accessing user layer that has not been registered : Matchmaking.Algorithm.UserId
What is the issue? Include screenshots / videos if possible!
My game has been experienced new bugs with data storage and messaging system, this may be related but cannot confirm.
Its probably an issue with the a new feature that is being tried out by roblox. It should be fixed in a couple of days, but shouldn’t impact too much of your developing.
If it is impacting your development, and you have evidence and know whats going on, then you can write a #bug-reports on it. Although this issue seems to be minor and I’m having this error and nothing huge is wrong for me.
Edit: Looks like its coming from IXPService. No information is found on the roblox documentation, but it looks to be handled by roblox and is a roblox made error