@martin_triska Thank you for this answer :)

As you can see the addresses of both MCP23008 are visible.

0x20 for the MCP23008 on the Unipi 1.1 board
0x22 for the MCP23008 of the EMO-R8 expansion board

And both boards have their own power supplies purchased from Unipi (CLW-1005-W2E-EB) of 5V in 2A.

And with or without, it doesn't matter...

So I made a new RJ11 cable and it worked :)

Life is simple especially with a good connection....