I’ve unplugged the thing completely from the mains and everything from all the ports and left it a while but when I plug it back in, it shows a red light on the front for a few seconds and then goes off.
Nothing wakes this up, not even buttons on the remote.
What can I do?
That suggests it’s booting but not showing a picture. Can you try another display and/or HDMI cable?
If you’ve enabled ssh and you know the IP address, can you connect via ssh?
I’ve tried both of these things but nothing changes. The front plus symbol on the box doesn’t light up white, it just stays un-lit.
Can’t remember the IP address for SSH either.
Have a look on your router to list connected devices.
Otherwise, it’s most likely the PSU has swooned. Do you have another 5v-2A PSU with either a barrel connector or USB (and a USB A-A cable)?
When did it last work?