sharepoint server – Adding items to a custom list application "silently fails"

Of Site Contents directory in SharePoint, I created a Custom List via New > App > Custom List.

I added 12 entries and everything worked as expected, the answers were visible in the list.

When you try to add following entries (when you click Save on the new registration form accessible by clicking on the + ), new entries did not appear in the list (even when refreshing the page).

It is as if the form "silently fails" and I don't know why.

It's a simple setup and worked for the first 12 entries, so I'm not sure why it stopped working all of a sudden.

For the context, I renamed the mandatory Title field at Organisation Name (because I don't need a Title in my form), so I don't know if this is a problem?