The inexpensive shop lights have a built-in ballast, and the ballast probably went out. The ballast can easily and cheaply be replaced, but most people (like me) will simply salvage the bulbs and replace the shop light with a new one.
Last spring, I got two new shop lights at Lowe's. I wanted to increase my total lumen output in the "Orchid" greenhouse. None of the two worked. The bulbs would dimly come on but never really light up. The ballasts were defective. Of course both of them were made in China. I took them back and replaced them with practically the same shop lights but from a different company. They worked fine and are still working fine. They were (naturally) also made in China.
I have eight shop lights, all like yours @ 4'x2 bulbs. They are all on timers, so the timer you used had nothing to do with the light failure. I now wished I had put in 4'x4 bulbs. Twice the lumen output but not a lot more expensive to purchase or to run. As these eight slowly fail (and they will), I will replace it/them with that 4'x4 fixture.
