The screen does not turn on.

We recently purchased a second-hand appliance that, unfortunately, was in poor condition. It was heavily soiled, with dried coffee residues inside, and we even discovered cockroaches within the unit. Despite this, the machine was still functioning initially.

To restore it properly, I carefully disassembled all components and cleaned them thoroughly. After reassembling the machine, however, it no longer powers on and the display screen remains off.

We would appreciate professional assistance in diagnosing and repairing the issue.