USCIS returned your filing without deciding it, because something about how it was submitted did not meet requirements. A rejection is not a denial: the case was never adjudicated.
What happens next
Fix what the rejection notice lists and file again. Note that refiling gets a new receipt date.
Official USCIS wording
On September 6, 2024, we rejected your Form I-485, Application to Register Permanent Residence or Adjust Status, Receipt Number XXXXXXXXXXXXX, because it was not filed correctly. We mailed your case back to you, including any supporting materials and fee. Please follow the instructions to resubmit your case. If you have any questions, visit the USCIS Contact Center webpage at www.uscis.gov/contactcenter. If you move, go to www.uscis.gov/addresschange to give us your new mailing address.