Section 17. All orders or decisions issued in accordance with this chapter shall be enforceable under section twelve unless and until reversed by a decision of a member of the board or a reviewing board, or a judgement or decision of a court of the commonwealth; and payment of compensation, when ordered, shall commence immediately, with the first payment to be received by the employee within fourteen days of the issuance of any such order or decision, and shall cover all periods for which compensation is due under this chapter. No penalties shall be assessed during the pendency of any appeal.