They may not be authorized to do dual agency, or they may not feel it is in the best interest of their seller client if a listing is hot since dual agency can get messy. 

Go to their caseworker (if you don't know who it is, look up the local office of '(city/county) Housing Authority' and call the office.

Power of attorney is not permitted, but I did have one lender who blessed off on a corporate resolution for a stateside entity member to have signing authority for the business.

Once you start negotiating with a tenant, all of your authority and credibility goes out the window. 

Barbara Corcoran — How She Turned $1,000 into a $5B+ Empire: PR Stunts, Sales Techniques, Critical Early Wins, Fighting Trump, and Becoming a Real Estate Mogul (#725) - The Blog of Author Tim Ferriss

You have refused to sign this form along with your ACH authorization form & W9 form. 

Definitely get with their broker and if you don't get satisfaction there, contact the state regulation authority for real estate licensing to file a complaint.

In my sub-markets, it is hard to get the Section 8 authority to move up to market rates.  

If the tenants try an end around by calling him directly, he tells them he cant do it without us authorizing whatever work it is.

I send the tenants a bank authorization form and set up a recurring receipt in QBO that charges them on the first of the month.