Httpout call return error UnknownIssuer

i use httpoutcall call my server .but return error
Call was rejected:
Request ID: ca3ee955847db661b116d2047936ccf6e41bd57c1a9265eae1c8a330e9e77edd
Reject code: 4
Reject text: Connecting to xxxx failed: Failed to directly connect: hyper_util::client::legacy::Error(Connect, Custom { kind: Other, error: Custom { kind: InvalidData, error: InvalidCertificate(UnknownIssuer) } });

It is normal for me to access this address with my phone. What should I do? My certificate is from the brand DigiCert and the algorithm is RSA