I've tried all the methods to try and restart the cable box and it won't start. The cable box upstairs and internet work fine.
"One Moment Please, Available Shortly, Ref code S0a00" and similar messages are generated by the cable box when the signal for the channel you are trying to watch is too weak or too noisy. This might be because of a problem at Comcast (check https://customer.xfinity.com/Secure/MyServices/, 1-800-Comcast voice response, or the "My Account" app) or a bad box, but is most likely due to a poor connection between the box and Comcast's network.
Troubleshoot by checking all connectors and looking for damaged coax cable. Running the cable through a surge protector, a defective splitter, or too many splitters can cause signal problems as well. If there is an amplifier in the line make sure it's getting power. You might also try unplugging the cable box/DVR/digital adapter power cord for a minute or so.
If you can't find the problem, call them at the phone number on your bill or 1-800-Comcast, or chat with them using one of the "Trouble" options at https://www.comcastsupport.com/chatentry/. Ask them to check the account setup and send a refresh signal to the box. If they can't fix the problem during the phone call, insist that they send a tech out to identify the cause and correct it.
If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (http://www.xfinity.com/spp/, about $5/mo). If the trouble is due to a faulty Comcast cable box/DVR/digital adapter or anything outside your home, you shouldn't be charged.
For additional information please see Pixelation, video and audio dropouts, One Moment Please S0a00 messages.
In my experience this happens when there is an emergency outage in my area. Nothing can be done tilll they fix it and usually they're working on it by the time I notice it. Only solution is a long run one to switch to fiber optic service. We have had Verizon FIOS in our other home for many years and haven't had one single outage.