Hi Aurore,
Sorry for the late reply.
Here is what you need to do to “… prevent clients to purchase more than 1 product from a specific category per month…”:
1. Enable “Per product category” checkbox in “WooCommerce > Settings > Maximum Products per User > Limits”.
2. Go to “Products > Categories > Your category > Edit” and set “Limit per user” option for that category to the amount you need, e.g. 1.
3. To add a date range (i.e. vs lifetime), you need to set the “Date range” option to either “Last 30 days” or “This month” (depending if you need it to be counted in the last 30 days, or starting from the 1st day of the current month).
Now regarding the “Order statuses” option – this sets when user order should be counted. So, for example, if you leave it at its default value (i.e. “Completed”), then the user will be able to make an unlimited number of orders until you mark any of his orders as completed – then his “quantity already bought” data will be updated, and he won’t be able to make any orders (until “Date range” option expires for him). If you will add all other statuses there (e.g. “Processing”, “Pending payment” etc.), his order will be counted at once. Hope that makes sense.
Now last note – in the latest plugin version 3.3.0 (released just a couple of minutes ago), I’ve added new “Order statuses: Delete” option to the plugin. This will restore, i.e. decrease “quantity already bought” for the user on selected statuses. So generally, such statuses as “Refunded” should be added here. In your case, however (i.e. you want to allow the customer to buy again when order is completed), you may want to add “Completed” order status here.
Hope that helps. Please let me know if you have any questions.