The U.S. Citizenship and Immigration Services (USCIS) has changed where you should file Form I-907, the Request for Premium Processing, when filed for a pending Form I-140, the Immigrant Petition for Alien Workers. Instead of sending it to the service centers, you should now send it to the appropriate USCIS lockboxes since December 15.
This change is part of USCIS's efforts to improve efficiency by reducing the workload at the service centers and lowering costs associated with handling Forms I-140 and I-907. It also allows USCIS to centralize the digitization of these forms for electronic processing. This is the second phase of a three-phase transition.
However, if you are filing Form I-140 along with another application like Form I-485, I-765, or Form I-131, this change in filing location doesn't apply to you. USCIS will announce a filing location change for these forms soon. For now, continue to file these forms with the service centers as listed on the Direct Filing Addresses for Form I-140, Immigrant Petition for Alien Worker page.
From November 13, 2023, USCIS changed the filing location for Form I-907 and Form I-140 to the USCIS lockbox (phase 1). Starting from December 13, 2023, USCIS will reject any Form I-907 filed with Form I-140 that is sent to the old service center address.
Starting December 15, USCIS has requested that filers use the new addresses when mailing Form I-907 for a currently pending Form I-140. Beginning on or after January 14, 2024, USCIS will reject any Form I-907 filed for a pending Form I-140 received at the old service center address.
Source: Original USCIS Link