Unable to activate hamstring muscle and knee pain

I cannot get a burn in my hamstring. I haven't been able to for a while. I have quite a loose joint capsule i think its called. I get knee pain when doing stretches. I know i do have a very tight hamstring, a hamstring contracture infact where i cannot stretch out my leg fully. whether that is causing the knee issue im not sure.
Does anyone know of any injury that can make activating the hamstring very difficult? I remember when my knee pain wasnt as sensitive, doing kettle bells and i couldnt get an activation/burn in my hamstring but did in my adductors, glutes, other muscles etc. this is in both hamstring/knees. i cant do any sort of hip flexor or quad stretch without knee pain.

If anyone could help that would be amazing.

There could be knee joint stiffness which is restricting its complete range or the muscle behind the knee, the popliteus. Or it could be your GLUTEUS. Get it assessed by a physiotherapist.