Cannot login through reverse proxy on new Pi4

my old Pi3 (which was working fine externally) got broke and so I have just purchased a new Pi4, I have installed the test build from Raspberry Pi 4 is out
logged in and completed config using local IP, All Good...

using my external access I get the login window, but when I enter the username and password, upon pressing the login button I get a quick flash of the shaded background with the spinning dots and I am then returned to the login window with the URL amended from to

So I believe it to be an issue with my Letsencrypt Docker NGINX setup, however, this was working fine on my old setup with a Pi3

is it the case that it does not yet work on a Pi4? or do I need to adjust my config somehow now I am using a Pi4?

if I use the local IP then it is functioning as expected

thanks for the great software and any advice in advance

Honestly, this isn't really about OctoPrint. I'm not sure if others here would be able to troubleshoot the complexities of your rig there.

Is it possible that you earlier were issuing a static IP address to that original Pi from your DHCP server? If so, then the MAC address has changed by the swap-out and the IP address would be different.

Hi, yes I have it all set to a static IP that has all been updated otherwise I wouldnt even be getting to the login screen. Hence why I was asking if the Pi4 is known to have issues due to OS changes for example.

Not that I'm aware of.