@najaals, Hi Naja,
welcome to the forum! I see this is your second post. So I hope you have already read:
It is a good idea to create a new topic instead of adding to a topic that has been quiet for some time. And to address all readers instead of a poster that may have been absent since then.
But you should add a link to your previous post, especially if it contains additional information:
Please always add links to the devices in question; the display board or panel and the connection board, and the processor board.
Your connection board may contain level converters and the "clever" reset circuit.
Please read the README.md of the library, it has remarks for this.
Please provide diagnostic output from Serial Monitor, so we can see if you have a boot mode issue, or if your SPI communication doesn't work. For this you need to use init with a bitrate, e.g. init(115200), to enable diagnostic output.
Make sure your wiring corresponds to the constructor parameters and to the HW SPI pins of the processor board; your comments correspond to the feather huzzah.
And make sure you did wire at all, not like on your picture! Don't forget VCC and GND.
Jean-Marc