My Vanilla cape only appears in Java Edition. I have my Copper cape in Bedrock, so some kind of error went into the system when I was getting my Vanilla cape. I didn’t report this issue years back because I didn’t really follow any Minecraft stuff on the internet. I tried contacting Mojang support 3 times but they put in crappy preset responses that say things like “sorry the cape promotion has ended and we can’t give you free capes”.
First Bedrock achievement was 6/20/2019.
No Vanilla cape in Bedrock, but Copper, which was redeemed many years later, shows up.
Founder’s, Pan, and Common all show up in Java. Vanilla is there too.
Java account created 12/28/2019.
We don't have access to your account, so we can't give you any capes if we wanted to. If Mojang Support won't give you the cape, then there's nothing that can be done.