playerCheck is a function which needs to be called in order to get the boolean result, i.e.: 
if (playerCheck() == true)
bool (*)() is a type for a function which takes no arguments and returns a boolean. 
playerCheck == true is an attempt to compare the function pointer with a boolean value, which leads to the compilation error which speaks for itself. 
playerCheck() == true is calling the function and comparing the result (of type boolean) with the boolean value. 
Note that if (x == true) can be generally abbreviated to if (x), so you could just write
if (playerCheck())
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solved operand types are incompatible (“bool (*)()” and “bool”) [closed]