What would make my platelet test come back invalid?

Patient: I went into the dr because I had numbness and tingling in my limbs, lightheadedness before eating in the morning. THey did all the blood tests and everything came back normal except they said my platelet test was unreadable or invalid. Bottom line is it didn’t work and I have to go back in. I also have some little red dots on me too. My question is what would make this test be unreadable?

Symptoms: Red little dots on my body, lightheaded and dizzy if I don’t eat right, numb and tingly in my limbs