Have you had to replace your power supply (12V 1.5A 5.5mm with 2.5mm + (pos) middle with -(neg) outside plug) for your S33 Modem?  Thumbs up is a yes.
I bought an S33 Surfboard modem on 4/8/2023. On 8/3/2024 it stopped working. Reviewing the community blog it became apparent that the power supply was the likely cause. I replaced the power supply at my own expense and the S33 started working again.