Are you sure that JupyterLab is installed in your env? I am not familiar with TLJH but from this comment there are multiple envs and you should ensure that JupyterLab is installed in User env
Are you sure that JupyterLab is installed in your env? I am not familiar with TLJH but from this comment there are multiple envs and you should ensure that JupyterLab is installed in User env