Pixel XL 128G, Android Nougat 7.1.2 - By re-indexing, I mean that you have to answer the front end questions (Do you want a public profile, etc.) as if it were the first time you'd ever used Verizon Messages. Not handy. Every other app seems to be able to maintain login and usage info after a restart. Just saying...
We have the same issue with two Pixels that just updated Message+ yesterday. I restart my phone several times a day, and this is unbearably annoying.
As for me, Message+ is uninstalled, and replaced with QKSMS.
The app updated this morning to 6.4.212. Still does the same thing on restart but the process is faster; seconds to be able to text vs. over a minute. Not the end of the world, but geez...Will take a look at your solution. Thanks.