It's been months. i don't understand. (minecraft issue)

so it's been about a month or two now, and i still can't join my friend's minecraft world on bedrock, i'm told (by minecraft) i need to "authenticate to microsoft services" I couldn't figure out the minecraft bug reporting app, and hoped it would figure itself out. it hasn't.
I've tried every single thing that could, would and should fix it.
I've reached out to Xbox employees.
I'm on a completely different computer now.
i can join servers, my friend (only friend on minecraft at the moment) can join me.
I can join public servers.
But i cannot join my friend.
my friend can't join servers, saying "Cannot verify login"
Don't know if it's me, or him, but it's annoying me, and on my end I've:

I've (on both computers) synced the time.
reset, cleared caches, changed values and such recommended by youtube.
Logged in and out of both Microsoft and Xbox, reset more.
synced time again
opened it via different launchers.
at this point i genuinely don't know what else to do, I'm very annoyed, and i used to have really bad internet so all of our worlds are on my friend's PC.

i don't wanna hear "Just transfer worlds" or "Just play on your connection" it's obviously something very broken and it doesn't make sense.

Hardware is an old HP work laptop (i think it's a note? i forget) and an Hp laptop 17.

:)