I am unable to set any tabs

Using Libre Office writer (x64)
Build ID: 98c6a8a1c6c7b144ce3cc729e34964b47ce25d62
In existing documents, here is no ‘tab’ tab on the Format -paragraph menu. Clicking on the ruler once or twice does not bring up the tab menu.
But if I create a new document both the above work.
Anyone any ideas please?

May be one out of many bugs in, I’d recommend to install the latest release. Just an comment, no real answer.

6.2.5. Same issue. No “tab” tab in Paragraph format window.

Note that the Tabs tab is hidden when paragraphs with different tab marks are selected.