Don't feel inadequate. As a daycare provider I often have the same complaint form my parents. " How come my child naps forever for you??? You must be magic!"
I'm not magic, but I am consistent and I am not Mommy and Daddy... Babies will always fuss more for Mom and Dad. Don't get me wrong... I have a gentle sleep program and I don't use cry it out in my daycare, especially for babies this young. Here are a few suggestions that have worked for me. Try to keep a consistent schedule... depending on how he sleeps at night and what time he wakes int he morning, try to put him down for the a.m. nap at the same time every day. Keep him active during the day. Play with him take him outside... keep him stimulated, but don't over do it. Nurse him or give a bottle someplace outside of the bedroom. Darken the bedroom as much as you can and try running a fan or a white noise machine. Have the room ready before you take him in to lay him down for nap. Do the same routine every time, whether it's singing a song or just swaying for a few minutes. When he fusses don't pick him up, just shh him and rub his back or head.
Good luck! They are smarties before you realize it, so the sooner they realize that their bed is for sleeping and you aren't going to go back and forth the better you and they will be.