The latest release of Message+ 6.9.0 was updated on my Galaxy 10 on August 8th. That matches up quite well with when the desktop version quit working.
Looked on my laptop, and I have the the following error/Failure in the event log:
Installation Failure: Windows failed to install the following update with error 0x80073D02: 9WZDNCRDCSNZ-VerizonWireless.VerizonMessages.
8/9/2019 10:08:34 AM - same day my cell phone verizon messages app updated.
Windows Update Agent