Add me to the list of users who, likewise, are experiencing 1-way sync with the MESSAGE+ app for Windows 10.
My gut feeling is that this issue will not be resolved, and, Verizon will drop the app. Microsoft's decision to discontinue WIndows Mobile and focus on bringing apps to Android and iOS seems to have triggered more developers to abandon the Windows platform altogether.
I hope this isn't the case here, but, it is now a "wait & see" situation.
This isn't about the Windows Platform for cell phones. This is about Verizon pushing their own messaging platform outside of the Google defualt, providing the ability to access it from their customers PC via a Windows or MS Store app (which allows someone to see emails on their desktop, and to create emails using a normal PC keyboard - which allows for more detailed and more accurate emails, and helps people with arthritis and other issues, and then breaking the PC side of the service with poorly supported programs and web interface. Verizon charges a lot but their support has been, IMHO, getting a lot worse. They break a major part of the service and then provide infrequent, vague reassurances that somehow all will be just fine some day, or month, or year.
I have not encountered any Windows Store app that works particularly well. As an example, a Speed test app that hogs CPU when not in use. Or this one, which is far larger than the V1.x normal Windows app but doesn't work very well, and doesn't have a force SYNC button.
Took this issue public to the Verizon FB page. This is their reply:
Verizon We are aware of this issue and apologize for any inconvenience this may have caused you. We have the network team engaged and working to resolve the Message+ issue. This should be resolved within 24hrs. - Alex
We will see. . .
Having the same issue that started on Saturday while I was using the hotel WiFi. I noticed right away that my phone and W10 Message+ was not working. Getting home is did not resume synching.
I can't find the OP that turned me on to this solution from last week, but I'd like to give him the credit for it. If you are fortunate enough to be an Android user there is an app on GitHub that works fantastic called android-messages-desktop (https://github.com/chrisknepper/android-messages-desktop) It will run in the background and minimize to the tray. It basically takes the android messages web interface and wraps it in desktop applicaiton interface. The developer is actively working on it and is probably wondering why he just got a big spike in downloads!
Anyway, you will need to go the "Latest Releases" and download the Android-Messages-Setup app.
Oh, and you WILL need to make Android Messages your default message app.