Lately Social Security has been sending initial disability claims filed online to a Workplace Support Unit (WSU), instead of the local field office. There are several of these WSUs around the country, set up to do overflow work. I have had initial claims filed online sent to various WSUs, including Boston, Tampa, and Birmingham.
Once assigned, the WSU has jurisdiction over these claims until they get to the hearing level, so all the things a local field office supports (such as processing your SSA-1696 and fee agreement, and associating you as Representative to the new disability claim file) need to be done by the WSU.
The field offices are set up to deal with inquiries. The WSUs, not so much.
Additionally, when an online claim is filed, the WSU may get in touch with the claimant to confirm that they are the person who filed the claim. They refer to this as an attestation. Sometimes this is by phone, and the claimant has no idea where the person from Social Security Security is actually calling from. So getting in touch with the right WSU can be something of an adventure, and may involve a call to the local office just to see which WSU has jurisdiction for the claim.
Once you know which WSU has the claim, you can provide them your 1696 and fee agreement. My experience is that it takes time, and usually a couple phone calls, for them to associate you as Representative with the claim file for a new claim.