Gunk will not clean off LP ?

I purchased a used Jimmy Smith LP that is absolutely scratch free but had an extremely dull shine to the vinyl. I clean all LPs with a VPI 16.5 RCM and Disc Doctor before play and that has always brought back the original shine to the Vinyl. This time it did not come back to shine and on playback sounds like the LP had been treated with something that did not come off in cleaning. After 2 cleanings it appears there still is some sort of treatment that had been applied and did not come off. It’s a great album but I am afraid to play it because whatever it is I don’t want it to gunk up my stylus. Any ideas on how to clean it off? Thanks Bill