When I am trying to insert records to Salesforce using ARC(OAuth2) getting below error Error: This session could not be mutually authenticated for use with the REST API

{
"message": "This session could not be mutually authenticated for use with the REST API",
"errorCode": "MUTUAL_AUTHENTICATION_FAILED"
}

403 Forbidden

But this working fine before. I getting this error suddenly.

Can anyone help me with this?

Thanks in advance