Electrical Questions? Ask an Electrician Online.
Welcome. My name is ***** ***** would be glad to assist.
It sounds as though you have purchased what is referenced as T8 lamps, where your older ones are T12.
The difference is the diameters and also the makeup internally.
Your old lamps use a completely different ballast in the fixture to ignite the gas than do the newer T8 energy savers.
You either need to get the original T12 lamps to use or you will have to change out the ballast inside the light fixture to operate the new lamps.
If you wish to endeavor into the new ballast change and wiring of the tube sockets, post the information on how many lamps in the fixture and your old ballast make and model so that a new one can be found to fit the fixture.
Let me know and we can continue to get you operating once again.