You’re most likely on WooCommerce. Products > Import is built into it, so there’s no separate plugin to name. That’s probably the confusion here.
Forbidden is a 403, so it’s your host blocking it, not WordPress. Nearly always mod_security. Ask them to check the log for the time you tried and whitelist the rule.
User Access Manager will do per user. Create a group, put just that one customer in it, then set the page to that group. No new roles needed.
Though if they’re already WooCommerce customers I’d skip all that and put it in My Account like you said. Yith WooCommerce Customize My Account Page (free) lets you add your own tab and drop the table in it.
Either way, check your caching plugin isn’t caching for logged-in users, or customer A can end up served customer B’s page.
