Stubborn
adjective
having or showing dogged determination not to change one's attitude or position on something, especially in spite of good arguments or reasons to do so. "a stubborn refusal to learn from experience"
Your dog won't do what you want? They are being as stubborn as a mule!
OR
...you have not taught them
...you have not trained for this situation
...they have not experienced this before and do not know what to do
...you have not got a good relationship with them - there is no trust
...you have not motivated them in a way that makes sense to them
...you have scared the heck out of them
... they enjoy conflict more than pleasing your boring human ways
...you have scared the heck out of them in this situation
...something aversive to them is occurring
... you have been unpredictable, and unpredictable is dangerous
...you have not presented your argument or reason well enough :p
... they are in pain
...you are rushing them
...they are not feeling well
...they are struggling to cope in the environment
...they are scared
...the opposition reflex
...you are angry so they are avoiding you
... you are losing patience and they are attempting appeasement because that is their priority
...you are the equivalent of brussel sprouts and the other thing is a fancy delicious sundae
...they are not misbehaving, they are doing what has worked for them in the past, which is what is most rewarding in the moment
So many reasons, but labelling a dog as "stubborn" is above all, not helpful. It is a human thing.
Let's get smarter, not rougher.
PS it is not lost on me that the word "dogged" is in the dictionary to help describe what stubborn means.