If the error you are seeing indicates a cipher spec mismatch, then try TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 as specified in
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
https://www.ibm.com/docs/en/ibm-mq/9.4?topic=client-cipherspec-mappings-managed-net