[SOLVED] Can find wired Ethernet connected Pi 4B on network

[Strider]

Can you download
https://www.advanced-ip-scanner.com/

And scan for your Pi? Sometimes routers can be a bit picky when it comes to handing out DHCP addresses especially if a switch is involved...

Just thought, can you ping it?

I’m on a Mac, so nmap it is. I can clearly see all the other devices on the network, but no Pi. I can see that the router has not givet an IP to the Pi, but the switch has established a 1000M link to it. I just tried a brand new ethernet cable, same outcome.

I can see that the Pi is lighting the red LED for about four seconds, and in the last second the green LED also blinks. Then both LEDs are off for three seconds, and then the cycle repeats itself. Anyone know what that is about?

NB: I think it must be the power supply that is not up to snuff. Voltage was good, but could be ripple or other noise. Will try another.

Ah, sorry - I didn't realise you were using a Mac. Good call on the PSU, a Pi 4 needs a good solid 5 v and current 3 amp for starters, also a decent quality PSU is a must - not necessarily a linear PSU either, ust one capable of providing the grunt.
To be honest I'd format the SD and use a newly downloaded image so at least you're onto a good start.
Good luck!