Thanks for posting and welcome to the Bose Community. I am very sorry to hear that you are having issues with your Cinemate Series 2 and would love to look into this further for you.
The system will power off after 30 minutes of no activity so please keep this in mind. I would recommend that you ensure that the power connection is securely connected as well as testing a different power outlet to ensure that this is not the issue. I would also highly recommend that you perform a reset on the system via:
Turn the product off
Unplug the power cord from the power outlet
Disconnect the Interface Module from the Acoustimass Module. Wait 30 seconds
Reconnect the Interface Module
Reconnect the power cord
Retest the system
Please update us on the result of this and if any other community members are having this issue or have resolved this issue please do let us know.