Who should I send the Notice of Intent to the owner or the property management company that hired me?

I run an S-Corp business. We refinished tub/tiles at a property in PA. We bill the Management Company for the work we completed. Apparently, the building is Owned by a Company out of NYC. Of the 12 invoices submitted only 1 has been paid. We now have 25K over 90 days old and 7K over 30-90 days old.