First, check that you exit correctly from WebTop after receiving this window, using the WebTop menu to exit (not the browser x ).
Then, if you have the possibility, you should check the webtop5 database, schema core, table user_settings.
Filter rows containing domain_id=‘NethServer’, user_id = ‘your-username-without-at’, key = ‘whatsnew.version’.
You should receive one record per service (mail,calendar, etc) contaning the value of the last version checked by whatsnew: when you leave “do not show anymore”, these should update to the latest version (visible hovering the mouse on the service button) - if these keeps staying old versions, something is going wrong while you close the “New features” window, in this case I will give you another clue.
Gabriele