Unable to add linear parameter to block

[Anonymous]

I've created a block of a double door. I'm trying to add a linear wall width and door size parameter in the block editor, but it's not not working. I can select the start and end points and would expect a parameter line to appear, but nothing happens. I can otherwise edit the block.

Does anyone know what's preventing me from doing? TIA

[Anonymous]

In the Parameters Manager, I was able to see that the two parameters exist, I just can't see them. I'm also unable to add an action to them as I can't select the parameter. I'm also not sure why the background is grey. If I start with a new diagram, the background is black.

[Anonymous]

The grey background is not relevant. 

[Anonymous]

I'm not sure what happened with the last drawing, but I started from scratch and it worked fine. I'm attaching the working block for reference.