Not able to join friends at all

Its been able a couple days now and i have someone who hasn’t been able to join us every time we invite them or send them a request it gives an error saying Unable process the request followed by the error (code 300036)

Any luck with this issue? My friend is getting this same error. @blizzard please help!

I am having the same issue trying to play with my Son. @Blizzard, what is the issue?

what are the platforms between the two parties? if they aren’t the same, need to make sure cross platform play is enabled. if on console, there may be settings that prevent party play.