This may already be known to some but if not I figured I would post here on how to play a stroke "Invite Friends" round for PC App vs. Mobile players. My Mobile opponent tried to invite me while I was on pc app and vice-versa to no avail. Invite simply never showed up on either side. We decided to try this and it worked perfectly. I got on Mobile and invited "friend" for a 9 hole round. On first Tee box, we both hit our drives. On my second shot as soon as timer started I immediately closed Mobile and launched the PC app version. Before completely loading it asked did I want to "continue" or "forfeit". I chose Continue and immediately joined my Mobile opponent to finish the game. If there is another way, other than coin rooms, please share. Hope this helps some of you enjoy rounds with Mobile Friends.
PS/ This was a Practice round with no coins involved. Even the putt preview showed up for both of us.