XPS 13 (9343), No bootable devices found

Dear all,

Maybe you can help me with my problem on my XPS 13 (9343). On startup, the is no SSD found, and therefore the Laptop will not boot (black screen with F1, F2, F5 menu in the upper left corner). All of these joices are not working, not a new restart, nor the restart and setup, or the diagnosis. With the last two solutions, I get the confirmation, that there is no Harddisk (SSD) detected. It ist stated (none).

I know that this seems to be a common issue, and I'm very interested in a quick solution.

Many thanks, Pat