Cannot connect to other friend's worlds or invite them

Hello,
I came to report a bug, which i hope is a bug.

Whenever me and my friend try to play minecraft together, it doesn't work. Because they either don't show up in my friends list, i am unable to connect to their world or the invite we send doesn't show up to the other.

We both have the same version of minecraft, the only difference is that i use MCPE on a Redmi X4 and they use the Windows 10 or the Iphone version.
The game worked for us in the past until suddenly it stopped working, i believe the version we were on before it stopped working was before the 1.13.0.1 version - when foxes came to MCPE. After that we could not play together, but only play singleplayer and we still can't play to this day.