The CNAME you created is only valid for shop.keydstars.com.br (exact match).
You will need to create another CNAME record for the www.shop.keydstars.com.br address as well, using either the full name, or just www.shop in the Name field.
→ Since your screenshot shows the record to be Proxied ():
Cloudflare’s Universal SSL covers only one-level wildcard, and will work for like shop.keydstars.com.br, but NOTwww.shop.keydstars.com.br, as that one goes one level more deep.
As such, you could be ending up with another obstacle, in your attempts to get www.shop.keydstars.com.br to work perfectly.
It does however look like the platform you use have generated a certificate so that www.shop.keydstars.com.br is also covered with them, but it may require you to set the Proxy status for the www.shop record Unproxied () / DNS-only, to work properly.
If I’m looking from my end, it looks like you may have set it to Proxied () now?
From my end, that hostname does however works fine now, although when trying to access www.shop.keydstars.com.br directly, it is currently redirecting visitors over to https://shop.keydstars.com.br.
That redirect is done in the same way as how you would do e.g. redirect from the naked domain (keydstars.com.br) to the www variant (`www.keydstars.com.br``), or the opposite way around.
The redirect seems to come from the store vendor (e.g. according to the set up, the operator of irrobaecom.com.br), and not directly form neither Cloduflare, nor Cloudfront which is also behind Cloudflare in it’s current state (and which irrobaecom.com.br normally seems to use).
Both shop and www.shop are sending me to the same content from here.
Otherwise, can you elaborate on how you’re still facing problems, and/or how it is still not working?
Any error codes/messages, any screenshots of the issue you can share, or so?