Cant see all the elements in the folder, only 20 showed instead of having 21

Yesterday i had the same problem of the guy in the link:

I can see only 20 elements in my folder despite having 21 in that folder an there is non navigation menu for the last element. If i change the view (es tabular view) the last folder is not displayed. There is a method to change the maximum elements i can see in a folder or how can i solve this?

Some elements might be hidden due to permission settings. I assume, you are looking as a Zope "Manager" or Plone "side administrator" (i.e. as a user who should have the required permission).

For its folder naviagation, Plone does not look at the real content but at the catalog (--> portal_catalog). Therefore, if the catalog becomes inconsistent (that can happen in some (usually rare) cases), the folder information might no longer be shown correctly. The ZMI (= "Zope Management Interface") for portal_catalog has a tab where you can check the information maintained for a content object (when I remember right, the tab is named Catalog); enter the path to the object in the "filter" input field (look at the display to find out whether the path must (or must not) start with "/"). If the missing object is catalogued, then updating the catalog (an operation in another tab of the catalog ZMI) could solve the problem; otherwise, you would need to recatalog the missing object (this is a bit more complicated; come back if it should be necessary).

Whit navigation menu i intended the navigation on the bottom wich allows me to change page.

i've just created a folder in a new site whit 21 folders inside and the same appears, i cant change page to see the last one because i dont have page 2

if i add an extra element i can correctly view all the elements

As already mentioned in the other post, the bug is causing this error. It's sad that it's still open...

I dimly remember having seen a post on this forum that could be related to a possible working on this problem (maybe from @thet ?) but I am too lazy to search for it. I was not following this forum 3 months ago so it's can't be old. Even if the bug is fixed on a developer's computer or in the current github code it's unrealistic to expect that the developer will lookup the 'issues' and close them once the fix is shipped to pypi. There are too many issues, if no volunteer steps up to janitor the issues list no developer will.

You can forget my supposition in my previous reply (catalog problems). Likely you see a presentation bug (when the last page would contain a single item). You could consider to file a bug report.