This creature does not need to be knocked out, it is a passive tame which means that you have to passively feed it by hand. This can be done by putting the food or kibble in your last hot-bar slot and pressing "E" (or "Y" on Xbox One) to feed it. Make sure to keep track of when it needs to be fed or else taming efficiency will slowly go down. The type of food you choose can also affect efficiency with kibble giving the highest and other berries giving the lowest. However, kibble can be harder to get in early stages.
Know that it is easiest to passive tame them, which means walking up to them and feeding them
Get a TON of berries, everytime you feed it, it will go up like 3-5%
Have a high speed, high attack flying dino, (high attack in case you "miss click")
HAVE PATIENCE, diplo's are a stubborn tame, they will push you playfully (hence the flying dino)
MAKE SURE there are no carnivores around, if there are carnies around it will attack it there is a chance of it dying, it will get rid of all your hard work, and most importantly, IT MAY DIE (R.I.P. attempted tame #1 + 2 😢)
Plz note I am not an "high level player" that has a giga, I am lvl 50, (51 at the time I wrote this, almost 52) so I am not that experienced, tho I am sorta, I don't know that much about the game
When your trying to dame it use majoberries bring at least 100 of them and some food u can use all berries but majo works best and if u don't have a crossbow and tranq arrows use passive tame which u just walk up to it and feed it but it will push you around so have a closed back wall to be safe and be aware of your surroundings