Steam invite issue

[Riamus]

I'm not sure if this is specific to this game or any steam game... Does anyone know what might cause an invite to not show the play button on the invited person's computer?  Basically, person A sends an invite and person B sees that they were invited, but instead of seeing the Play button, they only see a text line that says they were invited.  Without being able to see the play button, there doesn't seem to be any way to accept the invitation.  It seems that restarting both computers can fix the issue, but is there any other fix?

[Jugginator]

Sounds like an antivirus getting in the way, or just really spotty internet. Check the antivirus first