Product link_rewrite (friendly URLs) are usually automatically generated using product names.
There is an option in PrestaShop backoffice > Preferences > Products > Update Friendly URL, which should be set to ON.
If this is not the case, enable this option, unless you wish to set the friendly URLs manually yourself.
If the option is enabled, but link_rewrites on products are not correct, displayed like 'product' for instance, then this means that the option was not enabled at the time the products were created (all languages included).
When this option is enabled, the link_rewrite is automatically updated when the product name is modified.
Therefore, to update link_rewrites on product, the name needs to be modified.
To fix this in a easy and fast way, use Store Commander CSV export and import tools.
1. Your CSV export will include id_product and name EN.
Add more 'name' field for all languages you need to update. The language is to be chosen in the 'language column' of the mapping.
2. No modification is necessary in the generated export file.
Unless you wish to change product names.
3. Import the file. Tips: use the option 'load fields by their name' , and your mapping will be filled automatically :)
During the import process, we will modify name(s) on id_product (we delete to replace with the same names).
This modification will update link_rewrite on products.