Hi Fishmonger;
Welcome to the forum.
Sometimes there are some imperfections that remain on the connections during the manufacturing process.
Try plugging and unplugging the bypass plug several times. This sometimes works to help the plug seat properly.
Make sure that there is nothing blocking that connection ie: loose chips, dust (using a piece of steel wool or super fine sandpaper to clean the ends of your sensor cable works well).
Also; while the generator is on and the "E1" error is displayed and beeping, check the connection by wiggling the plug up and down and left to right. If the “E1” message temporally goes away while you were wiggling the plug, you need a new sensor connector.
Only do this step if you get an E-1 error when the sensor cable is hooked up - If none of the above actions work, the E-1 error may be a bad connection to the temp sensor the connection is located in the back of the smoke tower remove the back of the smoker and check the connection.