Shimano Logo Flashes but then shuts off

[Indigomacaw]

I’ll press the on button and the Shimano logo will stay up for a few seconds and then it’ll shut off.

the external battery when it’s not connected shows five green dots when I press the button on the battery. But when it’s plugged into the bike no battery level is displayed when I press the button.

I blew out everything with a compressor, no change. Where do you reckon I go from here?

 

[Highway550]

I had similar issue.
I removed the computer and cleaned the electrical connectors with a dry cloth (both on the computer & the computer housing). If the "turn on button" is on the computer, hold it in for a couple of seconds.