Often indicates the unit is powered on but may be stuck if it won't initiate a print job.

Be careful! While it can mean power is connected, a permanent solid green light during startup can sometimes indicate a "failed POST" or a boot error.

Has ‘greenlit’ been greenlighted? - Sentence first - WordPress.com

We often spend our lives waiting for a "sign" to start—a permission slip from the world telling us it’s okay to go. But the truth is, most green lights don’t just happen to you; you create them.