Custom 404 page not working (Blogger)

Question

So I wanted to make a custom 404 page on my Blog. I went in Settings > Errors and redirects > Custom 404 And pasted this Markup:

<h1 style="height: 0px; text-align: center;"><span style="font-family: Roboto;">Uh-Oh</span></h1><div><span style="font-family: Roboto;"><br /></span></div><h3 style="text-align: center;"><span style="font-family: Roboto; font-weight: normal;">Maybe <a href="https://www.youtube.com/watch?v=dQw4w9WgXcQ" target="_blank">This</a> is what you're looking for.</span></h3> Although I didn't get a custom 404. I still get "There's nothing here."
What am I doing wrong?

Answer 1

So @cyballruiz at Google Help helped me with the answer to this:

The theme you are using Soho Neon, have disabled the custom 404 field. It only show the basic/standar message 'there's nothing here'. What you could do is to edit your HTML theme and edit the following line of code: <b:eval expr='data:view.isSearch ? data:messages.noResultsFound : data:messages.theresNothingHere'/>

To solve this problem:

1. Navigate to Theme > My theme > Edit HTML on the blogger dashboard.
2. Search for <b:eval expr='data:view.isSearch ? data:messages.noResultsFound : data:messages.theresNothingHere'/> (Using Ctrl+F while text cursor is active)
3. Replace it with the code for your 404 page, in my case, which would be

<h1 style="height: 0px; text-align: center;"><span style="font-family: Roboto;">Uh-Oh</span></h1><div><span style="font-family: Roboto;"><br /></span></div><h3 style="text-align: center;"><span style="font-family: Roboto; font-weight: normal;">Maybe <a href="https://www.youtube.com/watch?v=dQw4w9WgXcQ" target="_blank">This</a> is what you're looking for.</span></h3>

[link to the og post]