[Rojofo]

Well, using the advice given me by Bluepeter, DNSB and others, I was able to update the internal firmware on the Kobo Glo. This SD was recognised by the Mac without any problem. When placed back in the Kobo the Kobo seemed to work perfectly with the update.

Unfortunately the update did not solve the connection problem. The Kobo recognises the Mac and reacts by proposing the connection and once the option is chosen, the message "connected and charging" appears on the Kobo screen. But the Mac does not display the Kobo which remains inaccessible, making it impossible to add books. The Wifi connection on the Kobo does not work properly and it fails to connect. It is strange that the internal SD card is recognised when it is taken out of the Kobo but the Kobo itself is not recognised.
There is no problem with the battery or the touchscreen. I have used an old USB hub connection but this Kobo is still not recognised despite changing cables and USB ports.

I am at a loss to understand this situation.