I've read several threads on this so I want to bring to Verizon't attention that the Message+ app is not reliable.
I will have text messages sent to me, either by individuals or as part of a group that show up on the phone but will not show up on the Message+ app. I have the latest version of the Message+ app installed on 3 PCs, 2 smartphones / tablets and I also use the web app directly on the Verizon Wireless website. The behavior is the same - some, but not all text messages successfully delivered to my Verizon phone never show up on Message+. There is never the case where a message shows up on a Message+ device that does not show up on my Verizon phone.
That's a problem. Please acknowledge it and get your application development team to fix it.
I have this same issue. It's weird since it seems to be a bit random on what messages it decides not to sync. Sometimes it takes 8 hours for a message to finally show up on the desktop/web app. Just right now I had a text with a friend who is also on Verizon; I was typing my replies via the message+ windows app and ready my friends text from my phone since my message+ app was not updating.
Several versions ago there was a sync button on the message+ on my phone that sometime forced an update on my desktop app but that has since long ago disappeared. I would gladly settle for having to manually trigger a sync from time to time instead of just waiting a random amount of time to see the conversation on my desktop/laptop.