You need to be more patient. Photos will have to scan your library for duplicates, and this will take much more time.
For my library with roughly 50000 photos and videos it took more than three weeks, until Photos has shown the first duplicates. This is taking so long, because photos is comparing the contents of the photos and is looking also for similar photos, not just exact duplicates. So it needs tor recognize the objects, the people, the scene, etc, and that requires a lot of processing. It will take even longer, if your library is stored in iCloud and the photos need downloading to be compared.
See: Remove duplicate photos in Photos on Mac – Apple Support (UK)
And note the caution at the top: "(Depending on the size of your library, duplicates may take some time to appear as Photos analyses your photos.)"
This is an understatement 😀
While you are waiting, check, if tehre are problematic items in your Photos Library. If you are having items in a legacy format in your library, that cannot be processed any longer on Ventura, Photos may not be able to check the photos for duplicates. If you are using iCloud Photos, you may be seeing a warning in the status bar. Check the status of your library in Photos for macOS - Apple Support