Getting signing cert for okta SPA app

Im using okta trial version and currently Im struggling to find a signing cert for my spa application. I followed the steps and I got the key ID but there wasn’t certificate for that key so can anyone help me to find the certificate ?

Do you mean JWKS? Are you using the Org Authorization Server? If so, the kid in the Access Tokens it issues cannot be validated locally as the kid will never match the one listed at the JWKS endpoint, as described here: Signature Validation Failed on Access Token | Okta Help Center