Ya, my friend (let's call him nick) had that same problem. Me and all my friends have been stoners for years, agreed to get nick high one time. well, he didn't get high that time. or the 2nd time we tried. or 3rd. Time after time, we couldn't get him high. Then, one day after my friend chris got off work, i took nick up there with him to get some bud. After me n chris bought an 8th each, we realized that these nugs were some of the best lookin nugs we'd gotten in awhile. So we proceeded to smoke nick out, and holy shit, we smoked like 10 bowls of this shit, i was so blazed i couldnt concentrate enough to read the caller id on my fuckin cell phone. Nick was so blazed, he was makin dumbass remarks such as "guys, are my legs supposed to feel numb?" and silly shit like that. of course, my legs to feel tingly when i get really high but thats another story...
anyways the point is keep trying, you'll get there.