Free sample limits

Hello,

I am having trouble limiting the number of free samples that a customer can order. I can limit it to 1 per order, but some people keep coming back in and reordering again.

I followed this from a prior thread in the help section:

General > Mode > Product Quantitites 
General > Date range > Lifetime (Or as per your requirement)
General > Order statuses > Select the relevant order statuses
General > Guests > Identify Guests by IP
General > Block guests from buying products > Block Method > According to limit options
Limits > Per product > Enable

However, this setup does not seem to fix it.

Do i need to check the “Block guests from ordering” box on the product page setup? Or does this block everyone? Also these are guests and do not have an account.