From September 30, 2020, all Web Services calls must implement HTTPS over TLS1.2 protocols.
SSL and TLS 1.0 / 1.1 will no longer be supported.
For this, and as indicated in the API documentation, you must replace the endpoint URL from "https://apis.synchroteam.com" to "https://ws.synchroteam.com". You may also have to force your development to use TLS 1.2.