I had access to the NEC when I upgraded my copy from the founders edition but now after the recent update it's not listed in game even though I own it on the Xbox store, and both the class 33 and 101 tutorial achievements are broken with the 33 it doesn't progress past the engine start process.
This might be a dumb question, but do you have a lot of routes installed? If so, some of them get pushed to a second "page" on the list at the bottom of the screen. If you keep pushing the d-pad to the right when you're in the route list it'll eventually flip to the next "page". For me, NEC is always the very last one listed. If that doesn't help, maybe try a hard reboot of your Xbox? Failing that maybe try deleting and reinstalling your whole TSW collection?
This happens to me all the time. Exit from TSW and re enter into it. If that don't work reset your Xbox.
For the missing content, just uninstall and reinstall it. I had this problem too and it resolved it for me.
Thanks I uninstalled and reinstalled content it is accessible again although the class 33 tutorial is still broken