Recently updated to Marshmallow... I am unable to get in-flight texting to work on my phone. I connect to gogo and select the "free tmobile texting" icon, follow all the prompts, and after cycling the wifi off/on, it will not connect to wifi calling. I continually get the REG99 error. After the last flight, I went to a physical store and they switched my sim cards and then called tech support. Their suggestion was to try it again on my next flight, but do the following steps: connect as normal, then "forget" the gogo network in wifi settings, reconnect gogo, cycle power...unfortunately that didn't fix the problem...I continually get the REG99 error and it will not connect to wifi calling which enables the free inflight texting...I had been using an S6 for a couple of months and it worked flawlessly inflight...without issues...I might add that wifi calling works perfectly fine at home and when using hotel wifi hotspots - never get the reg99 error.
The LG G4 has previously been stable, but the latest marshmallow update has ruined the inflight texting feature on this phone...As a side note, I noticed the same exact behavior using a Nexus 6 with marshmallow...it would display the same behavior as my LG G4 is doing...I wish that someone could run this up the flagpole and get it fixed.