I am using ST-LINK32/V2 with IAR. I connected it to my Laptop and to the board. Whe I try to debug (click Ctrl_D) I get a messagebox Fatal Error: ST-Link , No MCU device found.

[Mike_ST]

This can happen when your target MCU is not powered on.

ST-LInk V2 interface does not supply power.

[Ozone]

Can other software deal with that ST-Link ?

In former times, there used to be a "ST Download Utility", I think it's replaced by the "Cube Programmer" now.

Toolchains often come with outdated drivers for debug pods, so you might check the version, and try to update the ST Link firmware.

Your debuggee must be supplied by something - either externally, or the ST-Link.

In case of the latter, check if this option is enabled - and if the ST-Link is able to supply your board at all.

[SAran.1]

No, the problem is not the power.
Please note that the first time I connected the ST-Link, it was OK.
Then something happened, and since then I get this message.