Error message when sending an email from a shared mailbox

[learner38]

Hello, would need your support. I am getting an error message when using the send an email from a shared mailbox (having full access to the mailbos (editor+send as). Any suggestion?

Error details: "API is not  yet supported for this mailbox. This error can occur for sandbox (test) accounts or for accounts that are on a dedicated (on-premise) mail server"

[VictorIvanidze]

See https://support.microsoft.com/en-hk/help/4462988/rest-api-is-not-yet-supported-for-this-mailbox-erro...