3 years and waiting

It’s been over 3 years since I received my SOR after taking a FSP with an IC agency. 2 years since the personal hearing. The allegations against me for criminal conduct were exaggerated and did not reflect all the facts and circumstance but were framed in a way to put my in the worst light possible in regards to a dispute I had with a sibling. I heard that happens a lot after an FSP with this agency.

I recently inquired about the status and my attorney reached out to the agency but all that was conveyed was that no decision has been made. I also sent a letter to my congressman to ask if he could do anything.

How long can the agency wait before issuing a decision on my appeal?