Your stand up paddle is leaking at the valve and tightening the valve has not changed anything.
Prerequisite: The leak is located at the valve, and tightening the valve did not solve the problem.
Here are the steps to follow to install this seal:
Composition of the valve: Cap, upper part, lower part.
Step 1: Remove the valve cap then loosen the upper part of the valve using the wrench provided.
Step 2: Position the seal provided around the valve, cut it if necessary using a scissor.
Step 3: Center the valve and its seal on the paddle, taking care to avoid jamming the fibers on the thread of the valve, this could cause leaks.
Step 4: Tighten the valve using the wrench provided.
Step 5: Inflate your SUP to check that the leak is gone.
You will find a video link below to help you add a GASKET seal to your valve in the event of a leak and thus eliminate any air leaks from the valve: