Why does my internet service cut out after midnight?

It should Not. You need to call Comcast .

Check your parental controls and see if you accidentally set your wi-fi or internet to turn off after midnight. If you have x-Fi, you can check that as well.

It might be a setting on your router that lets you dictate when and if your internet shuts off for the night. You can set it per device or probably the whole router as it may be in your case. If you don't know how to get to this setting then call Comcast.

Not under normal conditions