Cannot boot my pi with umbrel

I followed all steps with the shoppinglist (exact as required), downloaded the latest version of umbrel, flashed it to my sdcard and setup my Pi4. It just does not boot. I tried different times and formatted the sd card and tried again. I logged in to my wifi router, but cannot find my device. I also connected my laptop with the cable to the router and used an ip scanner. Nothing. I am lost and also cannot find the answers in other topics. All stuff is brand new and never used before.
Can maybe somebody help me in the right direction?