For the answer to the question above,
There are some mistakes that maybe you've done.
Maybe,
You aren’t using landing pages.
You aren’t testing your landing pages.
You’re testing your landing pages the wrong way.
You aren’t building your landing pages for mobile devices.
People don’t understand what your page offers or what they’re supposed to do.
Your landing page loads too slowly.
There is no image of your product on the landing page.
Try to check these errors