First-time setup with SLOBS:

If you haven't used any external controller with Streamlabs OBS before, you will need to make sure that it can be remotely controlled.
In the main window, click on settings:

Then in the opened window, click on 'Remote Control':

Click 'Click to show' in the QR Code image:

At this point, you might get a windows security alert window, click the 'Allow access' button within:

Then you can close the Settings window by clicking on 'Done':

Should you have any other questions, please don't hesitate to contact me via email: