How to Make Header Full Width?

Yep, that's right.

Try this instead:

.site-logo,
.site-logo img {
    width: 100%;
}

If that doesn't work, can send me temporary login info so I can inspect exactly what's going on? That way you don't have to take your site public: https://generatepress.com/contact

Let me know :)

Doesn't work. I'll contact you through the link above. Thank you for trying your best to help!

Looks like you have the logo width set at 800px in the customizer:
https://docs.generatepress.com/article/adding-header-logo/

If you set it back to default, you shouldn't need Tom's CSS either if the image itself it big enough.

Ah, not sure why I didn't think of that!

There's a sliding bar, and 800px is the MAX it will go. I tried hitting the reset arrow button (which I presume is the "returning back to default" you are talking about), and still it won't go full width. Can you walk me through how to do this please?

Can you click reset so the slider goes back to this state:
https://www.screencast.com/t/dIHLJQX0i

Then click Published and see if it works?

I tried that after your previous comment, and then hit publish. No change.

So, then I went and disabled iThemes Security and Jetpack, then went back into the page, and hit refresh, and it was FINALLY full width! Then I turned iThemes Security and Jetpack back on again, hit refresh, and it stayed full width. Pheuf!

Maybe there was some plugin glitch happening? Or maybe my browser had the wrong information cached after resetting the logo width to default?

Either way, it's fixed! Thank you for helping! You have a great product & provide great customer service! Take care!

It could have been cached somehow.

Glad it's working now! :)