The equation should be in the form of $aT(\frac{n}{b}) + O(n^{k} log^{p}n)$ where a$\geq$1 and b>1 and k$\geq$0 and p is a real number.

If you can convert the given recurrence relation in this form then you can apply master theorem.

This version is used for divide and conquer type of problems like mergesort, quicksort etc

The extended master theorem is used for subtract and conquer, that is when the bigger problem is like sum of smaller subproblems.

it is of the form $aT(n-b) + O(n^{k})$

https://en.wikipedia.org/wiki/Master_theorem_(analysis_of_algorithms)#Inadmissible_equations

The above are some cases where you can't apply master theorem.