He has no idea what you are asking him to do

You need to show him and then praise him like crazy. First you need to get a treat that he thinks is heaven.
Try cheese or cheerios.
Sit on the floor at his level with a bag of your chosen treat. Hold the treat in your fingers and with your other hand lightly push his back end down and say sit while moving the treat back slightly toward his head. If he tries to take the treat from your fingers tell him no in whatever phase you use to get him to stop doing something he is not suppose to be doing~
When he does sit, give a treat and lots of praise.

This is not going to happen with one, two or ten treats. I spend 2 to 3 minutes several times a day and within a few days he knew what I was asking. If he got bored I just stopped and put the treats away. Do this several times a day until the end of this week. It will work-guaranteed!
Also, when you are trying to train him you
NEED to say and do the EXACT same hand motions every time or he will not know what you are asking him. If you plan to ALWAYS use your right hand for sit then this is what you need to do
every time.
Once he sits on command with a treat every time you then need to treat every other or every third times.
When he can do it without treats every time you can move on to paw. Tell him to sit do not give a treat just praise. Then lift his paw with your hand and say "paw" or whatever word you want to use and then treat and praise.
I taught Doodlebug first and Peebles decided he wanted the good stuff too, so when I told him to sit with the hand motion he just did it. Bogey (who we just got from a shelter a few months ago) learned very quickly from just watching the other two sit on command. When they come in from potty they all go into the kitchen by their cabinet and I can hand command each one and they sit and then get their treat. It's just so cute and when we have company over they always get a kick out of their little trick.
Once you get the sit down you can move on to paw and the whatever other tricks you want to teach them. Good luck!