You can choose how to display locked pages and inactive buttons to the learner, and there are several different configuration options.
When a page is locked, the Next (page) button will be visible to the learner, but will be shown in an inactive state until the next page becomes available. If the learner presses the inactive button, they will see the following icon, to indicate that this option to move forward is not available yet:
You can also choose to display a tooltip to give the learner more information about why the action isn't currently possible, by selecting the Show a tooltip... option shown here:
When the Show a tooltip... box is checked, attempting to use the Next button in its inactive state will display the default text 'You need to complete every part of the page before you can continue.'. This can be edited in the Text in your tooltip box and replaced with your own preferred text.
Link buttons will be visible to the learner by default, however these also have the option to show as inactive, with the additional information tooltip, by selecting this from the editing options:
When selected, the button will show as inactive until available:
It will display the tooltip if clicked:
As with the Next buttons, the text shown here is the default English text, but this can be edited.