I have an S7 Edge with mobile carrier EE. Since I recieved the handset it has never updated its software. The Nougat update has been live for months but my handset claims to be running the most up to date version of android. I have contacted EE and went through all the steps to fix the problem but they have now advised me to contact Samsung. I have tried a factory restore, firmware recovery via smart switch and was advised to dial *#1234# which showed up with the message 'Connection problem or invalid MMI code'. I have also tried connecting to Samsung Kies to see if I can download the update (or any update) via pc but it still shows as having the most up to date version installed. The Android version I have is 6.0.1.
I am building two s7 edge phones for my niece and nephew for Christmas. I have built and rebuilt dozens of the s7 edges and I occasionally come across a motherboard that will not update. I try the update periodically throughout the day or even several days and eventually it will start downloading the update. If your coming from 6.0.1, please understand that you have a long road ahead as each operating system needs to update before the next. Ie: 6.01 then all the various security updates then on to 7.0 followed by all the normal updates and then finally 8.0 followed by normal updates. This process takes some time but has worked every time for me. I have yet to find a motherboard that I cannot eventually update.