DIAGNOSIS That continuous beep is the generator's low oil alert. It's a safety feature that prevents startup if the oil level is too low or the sensor isn't reading it correctly.
FIX First, turn the generator off and let it cool if it was running. Park it on a level surface. Unscrew the oil dipstick, wipe it clean, and reinsert it without screwing it in to check the level. If it's low, top it up with SAE 10W-30 oil until it reaches the full mark on the dipstick. Make sure you're using the correct oil type. Screw the dipstick back in securely and try starting again. The beep should stop once the sensor sees sufficient oil.
IF THAT DIDN'T WORK If the oil level is fine, the oil pressure sensor itself might be faulty or have a bad connection. Check the wire connector going to the sensor (usually near the oil fill). Make sure it's plugged in tight and the wires aren't damaged.
HEADS UP Never, ever run this generator with the low oil light or beep active. It can destroy the engine in minutes. Always check oil before every use, especially after transporting it, as sloshing can trigger a false reading.