Hotkeys are established at level of an operating system and are the limited resource. It means that if one application uses the given hotkey another cannot take advantage to it any more for the work. Therefore sometimes there are conflicts. Hotkeys which be adjusted in TextLab by default can already are used by other programs or an operating system on your computer. In that case, in TextLab they will be marked as inactive, and will not operate. You can recustomize TextLab on use of other, not occupied combination of keys.
You can do different. You can recustomize use of hotkeys by other appendices or an operating system to release hotkeys for TextLab. Then to try to activate hotkeys adjusted for TextLab command Activate HotKey. To understand whom that is occupied and whether other combination of keys will help you Windows Hot Key Explorer (http://hkcmdr.anymania.com/)