WWE and Sting are no longer working together. This was revealed last year when an action figure for Sting was pulled from an upcoming Mattel line. It seems that relationship was not mended.
The company has now pulled all merchandise for The Stinger off their official Shop Zone website. You can search for it, but nothing comes up.
This is the same way that fans figured out that Brock Lesnar’s WWE deal expired. The contract was actually only through WrestleMania 36, but WWE had around 6 extra months to unload his merch. That time has apparently come for Sting and WWE pulled his merchandise.
Just because WWE pulled Sting’s merchandise doesn’t mean they will never sell anything for him again. They likely still have crates of Sting merchandise in their warehouse that they cannot legally sell.
Odds are they will hold onto that Sting merchandise and store it along with Brock Lesnar’s until a time comes when they can sell it again. You can never say never in WWE and it’s very likely that the company wants to ink a new deal with Sting for many reasons.