Why do the changes I put into custom.css not show up?

I’ve done some reading and understand that changes to css styling for GridMarket should be done in the child theme as opposed to the parent (FrameMarket) but when I put in changes in my custom.css file in the css folder inside of GridMarket theme files only a few of the changes I’ve put in place actually show up.

I’ve added all kinds of outlandish changes to see what works and what doesn’t so forgive that the site looks like a color wheel that lost it’s training wheels…but why is it that I cannot change things such as: background color behind “logo text”, color of the logo text itself, background of footer, nav colors???

And changing the base style seems to have no impact whatsoever on how the site looks with the exception of the hover color on the shopping cart button.

I’m not sure I understand what and where the css is being controlled from, or more importantly where to make modifications that will work for this theme….can someone please tell me how I can get control over the styling on this theme?