Utility Function Implies Consumption of Not All Goods
There might be a systematic way (e.g. some variation of the gradient method), but it is probably not trivial (see here), unlike this problem.

By checking $U(j,k,0)$, $U(j,0,s)$ and $U(0,k,s)$, you will find that one of them can actually never occur when utility is maximized. Then you can move on to examine the two goods where 0 consumption can occur, and compare their marginal rate of substitution to their price ratio. Whenever these are unequal in optimum, it signals a corner solution.