traytray:
The product IDs do not seem to be related to a product. ...
Based upon your "linked from", I'd guess you had a product (probably on sale) which was deleted or disabled (using the Zen Cart administrative interface or possibly because the store ran out of stock).
As gilby noted, one can check if there is a product with a specific ID by logging into the Zen Cart administrative URL and going to "catalog->Categories/Products". On the Categories/Products page you can type 2201 in the "search for" box on that page. Do not try searching from public facing "store" pages, search using the Zen Cart administrative interface.
If you do not have a product with ID 2201 (or product 2201 is disabled), a HTTP 404/Not Found will be shown for the product page. It does not matter if you are using the "stock" Zen Cart URLs or alternative URLs. In most cases these show up when: a product was deleted or disabled, a bad link exists in your sitemap, a bad link exists on social media, a bad link exists on a third party site, etc. Sometimes this also happens because someone was "browsing" your store and typing in "random" product IDs (or used an old bookmark to a product which was deleted / disabled).
If you do have a product with ID 2201 (and it is not disabled)... If my memory serves me right (I have not used that specific module for well over two years), CEON URI can interpret both stock and custom URIs (and will auto 301 from the stock to custom URLs)... So I would be surprised... And would say you would be best served posting some more specifics about what you are seeing in the CEON URI support thread...
Note 1: If the product ID does exist and is not disabled, make sure the copy of CEON URI is up to date... If it is, worst case, one could use a known workaround to add historic URLs w/o hand modifying the database... Just edit the product changing the URL first to the stock Zen Cart URL and then back to the custom URL...
**Note 2:**Your template is causing some 403 / Access Denied messages... May want to look into those as well...