Strange behavior switch knx

Tags: #<Tag:0x00007f173cfe98b8>

Hallo to all comunity, I’m a new openhab user and I’m developing a project with knx as binding. I made a connection with gateway knx and with it I made a item who send command to a group knx. This group simply turn on /off a light. A strange thing happens to me: Only command to turn on the light works. The command to turn off the light don’t work. I set it as a switch on both the channel of the knx device and the associated item. Have you some idea? Thank you.