Are you watching online, through the app or from a set top box?
Spectrum Social Media Customer Care
Forums Community Manager
For Media Center users, it is a known problem. Rovi, the source of guide data, has documented this to Microsoft and they are reportedly working on a fix.
In the past day, it appears that the "No data available" on some channels has been resolved. The problem with guide data existing only through 7/25 or 7/26, depending on your location, still exists. Normally, 2-weeks of data are maintained.
There is nothing you can do on your end to resolve this without switching to EPG123 and sub$cribing to Schedules Direct, their source of guide data. With any luck, Microsoft will impliment a fix prior to the data end date.