My friends are unable to connect to my Minecraft worlds but I can connect to theirs. Checked privacy settings and my Nat type on Wi-Fi etc. for some reason none of this works. One day it worked and the next day it didn't.

So basically my friends cannot join my Minecraft worlds and says for them  "unable to connect to the world" but I can join their Minecraft worlds. I have checked and changed my privacy settings on my Microsoft account so they can join but this has not resolved the issue. I do not know what else to do to try and solve this issue. May I please have some help. Kind regards