imo you're gone either too coarse to start with, or been too brief with a subsequent grit. The grit refers to the size of the abrasive particles. If a grit is say 400 in size, it will leave 400 sized scratches. If the next grit up is 600, the idea is use 600 until the 400 sized scratches are gone. If you leave 400 sized scratch, and keep going up, how are you going remove enough material to remove the scratch?
Despite a few BS claims out there of moving material around, abrasives remove material, full stop. The only way to get rid of a scratch (with abrasives that is) is to remove enough material to bring all the surrounding material down to the level of the bottom of the scratch. The reason for the progressive grits is to speed up the process.....but you never want to start too coarse or you creating deeper scratches than were there