if you can light it with a fireplace lighter or match or whatever, and its the FULL flame (not some tiny little worthless flame), it's NOT the regulator.
If its a little flame, do what Buckie said.
Did you replace the button portion of the igniter or the small white porcelain portion that screws into the tube?
The button igniters rarely go bad, they're just a pain in the butt sometimes.
The part that screws into the tube can be cleaned. Take it apart and gently clean it with some steel wool. Use a pipe cleaner to clean the inside of the gas tube as well. If its too dirty, rusty, or corroded, it won't spark.
I believe the screw that holds it down will need to be cleaned as well. (going by memory, as I no longer have an SS performer)