Brought a Rasberry pi 5 16GB today, unfortunately couldn’t get the thing to boot, the leds flashed but nothing on screen, tried Rasberry pi imager, misc utilities, bootloader pi family 5, sd card boot, after the green screen appeared, powered off inserted a new sd card with a fresh install of RPI OS, no joy, can’t put into worlds on how disappointed I am lol, hope you guys are having better luck, peace. Contacted pimoroni customer services replied saying they would get back to as soon as possible haven’t hear anything as of yet 
It is recommended that you provide us with the problem video so that we can help you analyze and solve the problem.
If the video memory is too large, it is recommended that you upload the recorded video to onedrive and share the video link with us and give us access to the link.
Does your PI5 work with the pironman5 chassis?
It is recommended that you remove the PI5 from the chassis, use a separate power supply to power the PI5, and connect the display to see if you can start the system normally.
What specifications of the power adapter are you currently using? Please tell us.
I’m using the official Rasberry pi power supply 27W, yes I tried the pi in the Pironman case same result flashing led, tried the board alone and again had the same result, I’ve built 2 projects in the past and never had any problems so not sure what’s happened this time round, hoping for a replacement or refund tbh, I’ll try get back to you with some feedback IE video. Thank you very much appreciated.
Since updating the boot loader after the green screen leds now flashing 3 times slow then 3 times fast.
No signal coming through to the screen.
Was planning on replacing the 8gb in my Pironman with a 16gb.
Your 8GB PI5 is working normally, but your 16GB PI5 is having issues and cannot operate properly?
From which vendor did you purchase the 16GB PI5? It’s possible that the 16GB PI5 has a malfunction, and you may need to contact Raspberry Pi’s official support for assistance in resolving the issue.