C++ nested class default constructor implicitly deleted?

I have a class with a struct inside it and I am trying to make an instance of the inner struct inside one of the class's member functions. When I do:

struct_type x;

I get the error: Call to default constructor which is implicitly deleted.

I didn't do = delete; and I tied to do = default; but I still get the same error. How can I get an empty default constructor for my inner struct?