light speed cache not working properly,

can somebody give me tips what to do , i have put the lightspeed settings but it doesnt seem thatit doesnt help me to fix the page speed vitals , like render blocking resources, lcp, main thread taking 4 seconds which is alot making my page speed score of 30 on page speed insights , even though i have light speed settings ok, but still it doesnt seem to improve the overall experience ,. somebody help me or give a tip to fix this issue