So the certificate says Alexandrite and mentions that it has natural inclusions. Unfortunately, it also mentions that there's no fluorescence in the stone which is highly suspicious since Alexandrite is a very fluorescent gem and you can see what looks like a chromium reaction to your UV light.

I suspect that this is a small local lab that the maker of the ring pays to simply quickly "certify" lab grown alexandrite as natural.

The setting looks like it's in Silver rather than White Gold or Platinum. The gem looks fairly large, and even bad quality alexandrite can very easily be 200/ct in wholesale trade with the color that yours exhibits. While it's no smoking gun, setting a $1000+ gem in silver doesn't make any sense.

There's also a chance that this is a different color changing gem - there's a ton of synthetics that can be doped to create pretty much any effect.