[Problem with text leading in Affinity Publisher]

I a a relatively new user of Affinity Designer and Publisher. In an effort to free myself from Adobe, especially InDesign which I use constantly as a book designer, I have signed up and followed several online courses in Publisher. Everything works except for one item, the leading on blocks of text. I really understand that leading in AFP is a Paragraph function, but on my copy of Publisher, running under macOS Catalina I am unable got make any visible changes in the leading of a block of text in a text frame, no matter what values I type in. Is there some secret to this? Is this a known if, hopefully, an occasional bug? Should I reinstall Affinity Publisher from scratch. Any suggestions more than welcome. Thanks. Lito