I got Spectrum yesterday and noticed that even though I have History and A&E on my package, and can watch them online, they won't show up on the channel list.
I also had problems with Discovery, Food, Animal Planet, HGTV and TLC all giving the error:
403 You've exceeded the maximum number of streaming sessions. To watch this program, sign out of one of your other sessions, and try again.: stream limit reached
If I manually rescan one by one after waiting a few minutes, it works.