Is the receiver by a land line remote phone? (can cause interference per what their tech told me).
Does the other sensor still work that is 200' away? (thought you had two, driveway at 300' and barn at 200'),
Are cars blocking the line of site between transmitter and reciever? With mine, didn't have a issue when there was only one car in the driveway, once there was more than one, it was a hit or miss as the cars were pretty much right in front of the house in the line of sight between the two. 1/4 mile model eliminated that issue.