Change in Number formatting, or my error?

Until recently, with help from this forum, I was able to format zeros as dashes by adding a third format code to the user enterable format codes in LibreCalc. For example: (#.##0);(#.##0);"-"));(@) or [>0]#,##0" “;[<0][RED]-#,##0;”–".
In a new spreadsheet created this week, none of them seem to work. 100 minus 100 equals blank no matter what I do: I can’t even manage to get a 0 out if it. I’ve tried "- " and some others too.
I’m guessing I’m missing a fundamental setting somewhere, but I’ve been duckduckgo-ing around looking for clues without any joy. I’d like to use dashes because they are easier to read than zeros, and indicate that I have not omitted or deleted a formula.
When I’m in flame mode, of course, I think that 6.4.1 invalidated this completely essential functionality (all caps of course), but in my heart, I know it didn’t. I just goofed somehow. Thank you all for the previous advice posted, and thanks again for input on this one.

Check if [x] Zero values is checked in Display group under OptionsCalcView.

Mike, that was exactly it - I found it there as you posted this. Thanks for the super fast response.

It WAS my error. I found the solution under Options in the Calc menu (not the general office menu): you select “show zeros” on the option sheet there, and all of zero formatting you define appears when appropriate.