It seems like almost every day now I have this issue.
Process goes like this:
1> Send invite request to invite+ world
2> Friend receives request and accepts it
3> Invite Notification never reappears on my side
This happens sporadically throughout the day and I can never really judge when it will happen.
An example of this can be shown from the timestamp 1h16m to 1h21m here: https://www.twitch.tv/videos/397038291?t=01h16m03s