Depending on the version of the module, the security hash may be missing and when this happens, indexing fails. You'll get the following error:
Your server is forbidding access to your feed. Please check file access and feed URL – [products][URL
When the URL of your feed isn’t updated in the Indices of Doofinder, it can also cause errors such as price mismatch, products missing, lack of updates on Doofinder side, etc. In any of the cases, the URL must be updated.
To fix this, go to your Prestashop Admin > Module Manager > Doofinder > find the Store tab and copy the corresponding feed URL:
Paste the feed URL in your Doofinder Admin Panel > Configuration > Search Engines > click on "See indices" > Indices.
Finally, reindex the feed by selecting the "Process Now" button, as you can see in the picture below:
After that, the error should be fixed or any updates carried on.
You might find it interesting to read about our Wrong Prices in Search Results and Product Not Showing Up documentations.