JWT Authorizer | Keycloak | Invalid issuer

I am trying to configure keycloak as a JWT authorizer in HTTP API gateway but I am getting the below error.

The configured issuer URL is: https://ec2-52-210-8-38.eu-west-1.compute.amazonaws.com:8443/realms/DUS

Invalid issuer: https://ec2-52-210-8-38.eu-west-1.compute.amazonaws.com:8443/realms/DUS. Issuer must have a valid discovery endpoint ended with '/.well-known/openid-configuration'

Knowing that I can access the ".well-konwn" configuration normally

https://ec2-52-210-8-38.eu-west-1.compute.amazonaws.com:8443/realms/DUS/.well-known/openid-configuration