I submitted my 1040x form more than 8 weeks ago and when I called they stated something was missing. When I mailed it in I also sent a copy of my w-2 and 1099 form. So what could be missing

I submitted my 1040x form more than 8 weeks ago and when I called they stated something was missing. When I mailed it in I also sent a copy of my w-2 and 1099 form. So what could be missing

What is missing, one of a 1000 additional forms depending on what you admeded
Did they tell you what was missing, have you gotten a letter on what was missing