Can certain players only get to a certain level? Ive filled the I guess 'bar' on my 26 QB bout 4 times and still hasn't made to 27, same with my 22 RB n 23 WR

Your player level depends on your championship level. Each level you progress the skill level will climb by 5 points

I would say any player can reach any level. And at the end of the season I have 10 points added to my max (last time it went from 50 max to 60 max). I do not know the specifics of your stats but I would guess you have not added enough to raise it one whole star. Maybe, and this is a guess, you have added points to Offense, Defense, and Physical/Mental (as opposed to just raising stats in 1 category) but it was not enough to raise any category up one star.

Players star rating is based on the average of all their stats. There are 25 different stats that can be trained so to get your player rating up by one star you need to assign 25 training points, this can be assigned to any stat or several different stats.

When you start the game on level 1 your players max stat that can be assigned to an individual stat is 40 and it climbs by 5 points per championship level

There is another thread on this as well. The admin states the formula as; Max player star rating = 35 + 5 * Championship level. I was mistaken in my earlier answer because I did not consider that I actually gained 2 levels both years; level 3 = 50 max and level 5 = 60 max. So the 5 per level is correct.