Product Permalinks Doesn't Work Externally

Hi,

When I switch to Pretty Permalinks option, the URL it generate will not work externally.

For instance, if I copy the URL on the product page which is on Permalink and share it to others. People will not be able to land in this specific product page, instead that they will land to the catalogue homepage.

For example: following is a link that was generated by permalink option (this link ends with a “?”),
http://oknames.com/domain-names/product/ipart.net/?

This page will land to it’s root page: http://oknames.com/domain-names/

Any solutions to it?

Thanks,

https://wordpress.org/plugins/ultimate-product-catalogue/