Your website mirrors each listing’s photos from your PMS on a sync. If you update photos in your PMS and the site still shows the old ones, the cause is almost always one of two things.
The photo sync has not picked up the change yet. Contact support to refresh the sync for your properties. The current photos then populate on the pages. This is usually a quick fix and covers all affected listings at once.
The photos are not on that listing in your PMS. If a listing shows only one image or a placeholder, check that the real photos are attached to that specific listing in your PMS. Once they are there, support can pull them through.
If only a few specific listings are affected, let support know which ones, and support will confirm each one.