Is it all TVS giving this error or just one TV?
775 error usually means a cabling issue on the swm network, or an issue where power inserter is not properly powering swm lnb. Unfortunately there is many places this problem can occur at, so I would suggest you schedule a service call with DTV and the tech should have no problem getting you back up and running.
But for fun if you want to check a few easy ones and maybe luck out here you go: check power inserter (small black box usually behind one TV with a cable coming in and out of it, w/ labels say "pwr to swm" and "signal to ird") make sure light is bright green and not flashing. Also make sure the cable fittings are completely tight on power inserter, the back of the receiver, and the wall plate where the cable comes from.
If no luck, you can try checking outside where the main connection is (either a switch, splitter, or ground block). Make sure those connections are tight. If loose possibly water from the storm got into the connection.
It could also be a shorted out switch, ground block, or lnb. That's why in this case best bet is to schedule a service call. But hopefully one of the first suggestions worked for you! Feel free to respond if you have any more questions.