G-Drive mobile is not mounted anymore

I use a G-Drive mobile for backups. This drive was operational until the day before yesterday. Now it seems to be dead. It is not mounted. The firmware update utility does not find it. If I open "About this Mac", it is recognized as USB device. But it is not recognized as a drive anymore.

How can I get it work again.

I can *not* connect it to another Mac. So please do not suggest something like that.

The configuration of my computer is as follows:

Mac OS Sierra

13" Mac Book Pro middle 2012

8 GB RAM

SSD hard drive with 512 GB