Error code 771 indicates that a DIRECTV receiver is having trouble communicating with the satellite dish, explains the DIRECTV Help Center. This problem results in a loss of television signal and sometimes occurs during severe storms.
A loose cable connection also sometimes causes a 771 error code. It is necessary to check all connections between the DIRECTV receiver and wall outlet, beginning with the SAT-IN connection. If all cable connections are secure, the next step is to cycle the receiver's power, which sometimes fixes the problem. This is achieved by unplugging the receiver from the electrical outlet for 15 seconds and plugging it back in.
If these fixes don't work, it is possible that the satellite dish is blocked by an obstruction. The dish needs clear line of sight to the sky in order to function properly.