did you try click add to cart anyways??
I see that too, but I was still able to add to cart
1. have phone in the cart
2. add a plan. Select current plan
48TB Node 304 / i5-3570 / Server 2016 Essentials
12TB HP Mediasmart EX 495 (E8400, 3.0GHZ, 4GB Mushkin), with Server 2016 Essentials
16TB Qnap TS-459 Pro
12TB HP Mediasmart EX 495 (E8400, 3.0GHZ, 4GB Mushkin), with Server 2016 Essentials
16TB Qnap TS-459 Pro