Hi all. I have a curious one here where my before + after spacing options are suddenly not working. They were working fine earlier today and I haven't updated or done anything out of the ordinary, but those options are mysteriously greyed out now. I can't insert the cursor into any of these. I've restarted and tried a brand new document. Not too keen to replace settings yet as I lose all my shortcuts every time. 😄
Maybe you accidentaly locked the layer?
Yes, empty value boxes such as we see in your menu are an indication that either nothing is selected, or that items with varying values are selected. Select one (1) paragraph and see if you can access and change its spacing settings. If not, I'd bet on a locked layer getting in the way.
>> Not too keen to replace settings yet as I lose all my shortcuts every time.
You should be making backup copies of those...
A few versions ago InDesign added a new option called "Space between Paragraphs Using Same Style" to the choices to be used for space before and after. Believe me, I feel your pain since the first time I encountered the issue that you're having I did freak out a bit. There is an easy fix, however, with the affected paragraph's selected, simply change the pull-down menu next to the option's icon in the Control Panel or Paragraph Panel to ignore. I see in your screen shot that ignore is actually chosen. Check to see that it is still reading as ignore when all of your text is selected. If not then change it. Also check any paragraph styles applied to make sure that the adjustment has been made to those as well.
I haven't seen this setting take away the ability to change top/bottom spacing, it just overrides it in the case of sequential paragraphs of the same style. Which, yes, can be confusing but I'm not sure it's the OP's problem; his settings box does say 'Ignore'...
ETA: ...but, he may not have the affected paragraph selected for that screen shot. This is a good candidate for the problem.