Homey 2019 flashed in all colours first - now only green and blue

Purchased a used Homey Pro 2019.

When first connected to power, it displayed seemingly all colours.

Now blue and green at the same time.

Is not found by my smartphone and cannot be reset.

Any advice?

Thank you.

I’d start with a factory reset;
From the knowledge base:
https://support.homey.app/hc/en-us/articles/360024602314-Resetting-Homey-Pro-2016-2019-to-factory-defaults