Makerbase Robin Nano 3.1 won't flash

I assume you mean Voron Trident, and I would strongly encourage you to return that kit or sell it. That printer requires a strong understanding of 3D printers in general, and Klipper in particular. Reading through this thread I don’t believe you’ll have a good experience with that printer kit.

In case you’re curious, the documentation for that printer is online (Voron GitHub).