I can add the trådfri outlet but i does not turn it onn and off. Why? It shows under Home–}all devices
Actually now i could turn it on, but it say: Failed to controll 99% of the time , now i cant turn it off

Please note that Zigbee is a low-power wireless mesh network standard. Within it there are several platforms (ecosystems) and this means fragmentation. Interoperability of devices from different platforms is not guaranteed. This is the case with your device from Ikea. A reasonably up-to-date list of devices supported by iHost is published at https://appcms.coolkit.cn/uncategorized/16355.html, once the Zigbee2CUBE add-on is installed.