Here is what I can tell you from a quick look at your player.
First of all, if you are training his Inside Shot (IS) or Inside Defense (ID), then you should single-position train him at that skill. This means that you set it to only training Centers, and play him at C for that week. If you are trying to train Rebounding (REB), then it doesn't matter if you play him at PF or C, since REB only trains PF/C or the whole team.
One thing to note: The more positions that get training, the slower it takes to get a pop. You only get 70% of the total training of single-position training if you do 2-position training. And that is assuming that you have gotten at least 48+ minutes in that week.
Second, you aren't playing him enough minutes at 1 position. This season, you have either played him too many or too few minutes in a week. In order to keep his Game Shape up (as well as your other players), and give him better chances to pop, you need to get your player 48-75 minutes per week. The general consensus is that the best amount of time you should play your players per week is from 50-60 minutes. When you train players in general, a rule of thumb to follow is that if they play less than ~43 minutes in a week at a certain position, switch to 2-position training, as long as they have minutes in other positions.
Example:
40 minutes at PG, 20 minutes at SG. Good training choices are 1v1 Guards or Jump Shot (PG/SG).
35 minutes at PF, 15 minutes at C. Good training choices are Rebounding (PF/C).
This week he has played 30 minutes at C. Another 18 minutes at C this week, and you can train him at full training at IS or ID. I would advise you to train him REB this week, as it is low for a player at his position.
One last thing I will tell you is to train his secondary skills (guard skills for bigs, inside skills for guards). Since you are beginning in the lowest human division in Australia, I would also train his Outside Defense (OD), Handling (HA), and if you want him to be able to make a jump shot here and there, Jump Shot (JS). I would get his OD and HA to at least inept (4), and you can decide how high you want his JS.
Sorry for the long post. To summarize, single-position train skills that can be single-position trained, play your players 48-60 minutes per week for the best chances of good Game Shape, and train his secondaries.