The warranty scanning used to be really good a few years ago, but I think HP started really restricting it. Seems like you can only look up a couple at a time before it starts blocking you.
I've registered for the HP Developers so I can access the warranty using the API, but that doesn't work for servers since the split and now we get this on the warranty API page at HP:
Please note: The beta Warranty API is currently unavailable.
We will resume operations at a later time.
For small numbers of devices, please consider HP Support's manual Warranty Checking web form.
So all-around terrible when looking up HP warranties.
None of this is really LANSweeper's fault, I think they are doing the best they can with what HP is providing.
Luckily we only use HP for our ESX host blades, so manually looking up and populating the warranty dates for 10-20 new machines every year isn't too onerous.