My son has white( polyester )cricket shirts that have yellow/brown stains around the collar/sleeves where he wears sunscreen. Normal detergent and napisan wont remove, either soaking or as a paste. Gets worse each week. Have also tried vinegar on a couple of them.
280400cookie-checksunscreen on polyester cricket shirts
Get some Kenco from Bunnings and use it as a spot cleaner. If that doesn’t work try Ajax Spray n Wipe with lactic acid
Try oven cleaner, spray on, wait 5 minutes. The oven cleaner should convert the sunscreen to soap by a chemical process call “saponification”, it will then just rinse off.