The SG400 and SG800 printers have an Auto Off option that is, by default, set to Active. This means that the printer will automatically power off when it detects no activity on the network or USB port.
As with all our sublimation printers, we in fact recommend that the printer be left powered on at all times. This is in order for the printer to perform its automatic maintenance which will greatly reduce the risk of ink drying and thus blocking the print head.
In order for the printer to remain powered on, you may need to set the Auto Off function to Not Active. This option is located with the printer menu > System > Auto Off. Once the option has been changed, you will need to restart your printer.