I have been having a similar problem with two Samsung tablet: one 3 year old 8.4 inch model and a new 9.7 inch S2. No matter what I did the go app would only display the "Enter Device" button and that button would not change to "Go Fly". Maybe once in ten or twenty tries did it work. My Samsung Note 4 smartphone, two years old, worked no problem but the tablets did not.
After a little poking around I found that by enabling "Developer Options" and going to the "USB configuration" setting I could change the setting to: Charging, MTP (Media Transfer Protocol), PTP (Picture Transfer Protocol), RNDIS (USB Ethernet), Audio source, or MIDI. Initially it was set to MTP and when I tried changing to PTP there was no effrect. I then tried RNDIS and immediately the Go app displayed the "Go Fly" button. When I went back to developer options the setting had automatically gone back to MTP. I think what happenes is that when you change it to RNDIS it tries that but immediately revert to MTP and I think doing that is a kind of reset.
So, this is not likely to be a Samsung problem as it appears to happen with other companies devices as well. My guess is the DJI has once again not done a great job in coding and hopefully they will rectify this soon. This is likely to require a new RC firmware. Fortunately, all I need to do is go to developer options, toggle the RNDIS on and that resets things so I can Go Fly.
BTW, the recommendation in post #2 did not work for me.