Your favorite search engine ("41A4315-7D error codes") is your friend. According to this page, 4 flashes means that the safety sensors (at the bottom near the track on each side) are misaligned. The same page says that to fix it, you "Realign the safety reversing sensors so that the LED on the receiving sensor glows steadily."

Very common problem - accidentally hit sensor with foot, garbage can, etc.

Too bad the OP didn't return.