Unable to display navigation during Tech Document Challenge

HTML-CSS
1

Tell us what’s happening:
TLDR: The navigation bar is not displayed 100% of the time (according to the challenge checker).

Longer Version: I am trying to pass 1 of the tests “layout 1.” from the Tech Document challenge, which states I need the navigation to be perfectly visible no matter what device is using the site. It works on the full screen, but while resizing I can get different results. I am in need of assistance with understanding how to fix the issue and perhaps understand more about developing a proper navigation bar.

Any tips, tricks, advice is welcome and wanted! If something sucks let me know, ill try to improve and fix it but ill probably need an example since I am struggling to understand. Thanks very much.

Your code so far
https://codepen.io/smashtrees/pen/XWmwjYR?editors=1100

Your browser information:
Mozilla Firefox.

Challenge: Build a Technical Documentation Page

Link to the challenge:

2

Layout test 1 is supposed to fail on small viewport sizes (below 868px), it’s as expected.

Test message:

Please run this test in a larger window (before any media queries) : expected 850 to be above 850