Status Code 225 is displayed by a digital adapter (DTA) when the signal for the channel you are trying to watch is too weak or has too much noise. 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 DTA, 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 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 DTA. If they can't fix the problem remotely, you might try swapping out the DTA at a Service Center (check locations and hours at http://customer.xfinity.com/service-center-locations). And if that doesn't work, insist 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 $6/mo). If the trouble is due to a faulty digital adapter or anything outside your home, you shouldn't be charged.