CSS code to display menu in horizontal is not working!

[mxpweb]

I was following an online course, wordpress theme,
This css code was to display the list menu in top to be in horizontal:

header .top-bar  {
    list-style-type: none; 
    margin: 0;
    padding: 0;
    display: flex; 

But this did not support to display the menu into horizontal and remained vertical,
Any idea is the code is correct or something else missing?
Thanks in advance.

 

 

[Ingolme]

That should work, if .top-bar is the <ol> or <ul> that contains the list items.

[dsonesuk]

I presume you've made adjustments to php code so the menu is positioned correctly within html to produce horizontal menu? media queries that adjust menu depending on device maybe a factor also.