OPM write back?

I wrote you the OPM for my appeal. Does anyone know how long it takes to hear something back from them?

No, I've never heard of OPM?

I got denied my BCBS federal, so I had to write an appeal to the OPM. The OPM is the Office of Personnel Management and they maintain a database for nearly all of the federal government , like a big Human Resource for federal employees.

What was the reason for their denial? I have BCBS federal and had the surgery on May 25 with no problems from them.