Subscription Passcode keeps dropping

We have a paid subscription to Construct 3. we have a secret access code that must be inputted into the users account so they can access full blown Construct 3. Routinely the access code drops out on the users, even after they check the 'remember me button'.

Why does this code keep dropping? is there a reason behind it dropping? can we stop it from dropping?

It's saved to browser storage, and so it will remember it as long as the browser does. If you clear browser storage, or the browser privacy settings are set to do something like clear storage periodically, then that will also clear the saved access code.