I've tried different products but no luck. Not sure what caused that stain.
Kool aid lemon aid
Have you tried baking soda and vinegar? Clear most of the water in the bowl then put a paste of baking soda and water along the line. Spray it with vinegar and let the whole thing soak. You can soak a paper towel in vinegar and stick it on top of the baking soda. After a few hours, scrub and it should come right off - especially if it's hard water stains. Flush and rinse. Another method that has worked for several people is to add Alka Seltzer to the bowl and let it fizz. Scrub and rinse. Wishing you the best.
Coca Cola. Not diet. Pour it in and let it set for a few hours or overnight.
Lysol Toilet bowl cleaner with rust & lime remover, comes in a black squirt bottle. Scrub with Scrub Daddy or Mr. Clean Magic Eraser.