When the monitor can't find a supplier that have the item in stock the item / listing will be putted in protected mode.

Note that in some cases , you will see that the product appear to be in stock on Amazon, but item will still be in protected mode , due to the fact that the supplier didn't qualify to your expectations ( based on your configuration )

You have a video in the dshopit site for all the reasons why items are getting into protected mode even though they are available on amazon

http://dshopit.com/members/en/training 

Video 8 - Why an item is out of stock