Unable to configure mutual TLS configuration of Custom domain names configuration of API Gateway.

I'm unable to configure mutual TLS in "Custom domain names" option of API Gateway.

Below are steps I have followed to configure mutual TLS configuration: I have a root account and its child account.

Root Account Steps:

1. Created a new client certificate using "client certificates" option of API gateway in root account.
2. Downloaded the new certificate. the new certificate file name is qde1ca.cert. Renamed the qde1ca.cert file using mv qde1ca.cert gateway.truststore.pem.
3. uploaded gateway.truststore.pem file to a directory application-truststore of S3 bucket of Root Account. The S3 bucket name is integrations-us-east-1. The directory has version enabled. So, my S3 file path is s3://integrations-us-east-1/application-truststore/gateway.truststore.pem
4. Noted Object URI and Version ID of the newly uploaded gateway.truststore.pem file.

Child Account Steps

5. In child account, I tried to configure mutual TLS of Custom domain name of API Gateway.

   • enabled Mutual TLS authentication option
   • Configure Truststore URI as the Object URI (s3://integrations-us-east-1/application-truststore/gateway.truststore.pem)
   • Truststore version as Version ID of the newly uploaded gateway.truststore.pem file.

6. Saved this configuration.

When I test using Frontend that invoke APIs of API gateway, it seems that the APIs are not executing. However, when I reset the mutual TLS configuration using OLD values Object URI and Version ID, The APIs in API Gateway works correctly!!!

What am I missing into the new mutual TLS configuration of Custom domain names configuration of API Gateway?