Why does Shift+F4 not work in Libreoffice calc version 5.2.5.2?

When I use Shift+F4 to change a relative address to an absolute address, nothing happens.

Look in Tools | Customise and click on the Keyboard tab. Scroll down and make sure Shift-F4 is linked to Relative/Absolute references; if not that function can be found under the Insert category below.

For the new version, just use F4.

From version 5.1 (see tdf#59418).