If you are experiencing that your PLAATO Airlock stops bubbling when you place your PLAATO Valve between your fermenter and the airlock you properly have a leak. There are a couple of things you can try, to find the problem.
Check that the PLAATO Valve is mounted correctly in the fermenter and that the PLAATO Airlock in mounted in the PLAATO Valve. To check for leaks you can spray some star san around the connections to see if any Co2 is escaping from the sides. If you see the star san bubbling you properly have a leak there.
Unmount the PLAATO Valve and spray some star san on it around the check valve on the size. Block one end with a finger and blow air into the PLAATO Valve. If you see any bubbling there is a leak in the PLAATO Valve. This may be fixed in the third step.
Screw off the check valve on the side of PLAATO Valve. Check that the gasket is whole and sits correctly and is not warped. Also, check that you have a filter in the valve. See this video for how to correctly assemble the parts of your Valve
Screw on the check valve again and make sure it is tightly fastened. Repeat Step 2 (above) to check for any leakages.
If the issue has persisted after going through the checks, please write into firstname.lastname@example.org or through the messenger app at the bottom of this page.
Let us know what steps you have taken and the results.