I've successfully using Message+ app on my Samsung Note 9 and Galaxy S6 tablet on Verizon service.
Yesterday I changed providers. I have read here that Message+ will work with any wireless provider. The change in provider caused me to be logged out of Message+ on my tablet. I was required to request a QR code to be read by my tablet to authenticate the tablet to receive text messages. I did this four times and each time the tablet error message was that the QR code was not valid. What's the secret to authorizing my tablet on my account?
We are saddened to hear you have chosen to go to another carrier. It concerns us to hear that the Message+ app is not working for you on the new carrier. Our support for the app is limited even for those who are using Verizon Wireless, and more limited for those who are using other providers. Higher-level support for this app is provided directly by the developer. Here is how to report it. Open the Message+ app. Click Menu > Get Help > Report a bug. This action will alert the developer to the issue, and they will take it from there. Does this information help?