Can users log into a protected category by clicking on a link?
The Password Protected Categories plugin comes with 2 types of protection: password protection and private categories. You can only log into a password protected category by manually entering a password on the category page or a central login page. However, private categories work with WordPress user accounts, which gives you more flexibility.
If you want to let people click on a link to automatically unlock a protected category, then you can do this by using private categories with the free Autologin Links plugin. This lets customers log into their WP or WooCommerce account simply by clicking on a link to a secret login URL. It then logs them into their account automatically without having to enter a username or password.