How do I connect a laptop and dekstop computer via ethernet cable on Windows 10?

I used to be able to do this following this guideline in Method 1:
https://www.wikihow.com/Connect-a-Desktop-to-a-Laptop

When I set that up, I was able to connect my laptop to my desktop via Ethernet cord in a fingersnap.

My desktop is suddenly unable to detect my laptop when I have my Ethernet cord connected. My laptop detects my desktop but then says there is an error in connecting.

I tried following the guide in the link again but it was already set up the way it was years ago. The only thing I ever deviated from the directions was use subnet mask 255 instead of 225. For some reason Windows 10 didn’t like it when I used 225.

I just had a Windows 10 update on my desktop, so. . . I have a feeling it has something to do with that.

Windows troubleshooter is about as useless as a third nipple.