Solved Unknown error preventing game from loading

Hello there,
Those lines aren't error lines. They're telling you that the OS is supported and the 304 responses mean that the game was able to successfully connect to the website, files are up to date and there is no running game instance. First thing to do is read the troubleshooting tips from our website added on the join page and check this thread out as well.
I'd suggest you remove any current game clients you may have on your computer and download the portable game version from our website. Next, extract it into some new folder like D:\Diablo2, download the realm patch from our website and extract it's contents inside your game folder then run the executable files as an Administrator. If you have any antivirus, windows defender, etc make sure to add the whole game folder to exceptions lists. Don't turn those off, just add the folder to exceptions list. I got your previous message too, will take a look a this through remote assistance.

Fixed, easy steps below:
1. Uninstalled previous game client
2. Reinstalled by downloading portable game version from our website and extracted contents into a new folder
3. Compatibility and Run as Administrator was set for executable files and the game folder was added to exceptions list inside windows defender (optional)
Removed some lame protection software called Advanced System Care that was installed automatically by Cnet, any free antivirus such as Avast will be a million times better.

PS: Welcome back!