Turn around and walk backward about ten feet every time you feed it berries then turn back around and see which way it turns and then sneak around it, feed it berries,repeat EASY TAME (by the way remain crouched the whole time and have LOTS OF PATIENCE!!!)
Always stay crouched while taming. And never get close enough to touch it. While following the monkey, if the monkey ever stops, its very likely It will turn and start to walk in a different direction. So be aware that it might walk in your direction. Hope this helps : )
First thing I tamed. Raptors jumped me I died, went back couldn't find it. Fast forward 2 MONTHS, find it in front of my house with a Rex bone helmet and a Spino egg along with some berries (I had wandering enabled). Loss of words.
You can place helmets on it too. I place my mining helmet on my monkey and use it as a source of light at my base. But you cannot see the light if the monkey is on your shoulder and your looking in first person. You can see the light in the orbital camera, While riding on another Dino in 3rd person, and when the monkey is on another persons sholder or on the ground. Hopes this comes in handy : )