Another fluorescent light question
You're much better off with the (did you notice, much lighter) electronic ballast.  Instant start is fine, since it's the only type possible with 1-pin ends.  

There are only 4 parts to a fluorescent lamp: Chassis, lampholders, ballast and lamps.  You just eliminated ballast.  Lamps, I'm trusting you here.  That leaves lampholders.  

Look at the lampholders closely, make sure they are intact and the jumper between the yellow lampholders is intact.  8' 1-pin replacement lampholders can be had for a couple of bucks, I replace them all the time.  (4' 2-pin lampholders are like 60 cents.)