https://www.copyright.gov/registration/docs/processing-times-faqs.pdf

"The Copyright Office’s processing times vary based on a number of factors, including how difficult a claim is to review, whether
an applicant submitted a physical deposit, whether the Copyright Office needs to correspond with an applicant, and the number of
registration specialists available to review claims. For example, claims take longer to process when applicants submit online claims
but do not submit physical deposits when necessary, or when applicants do not fully respond to an examiner’s questions. The Office
encourages applicants to refer to the Compendium of U.S. Copyright Office Practices and the Copyright Office’s circulars prior to
submitting applications to avoid unnecessary delays and correspondence."