Same for me! It happened by chance, I wanted to clean up a little bit the mess on this PC. After reinstalling Unreal I got some issues, all of them related to .NET packages.
Searching for a solution I fond out many other users got similar issues.
I really hope this might help because I’m out of ideas. 
Still stuck at 0%, this is really annoying. I’ve installed both but it unfortunalety doesn’t help
Hrm, for the most part I’m out of ideas, if the installation was successful but it just won’t get past that point in the launcher, it’s being blocked by something specific that we’re likely not privy to. If the launcher is at fault and the original installations failed for corruption or any other reason, and reinstallations don’t help, we’re left with an official bug report as our main course of action. Sorry for the inconvenience!
How long does it take till I can expect a response?
With bug reports it’s more about getting the info to the team to see if it’s something on the installer’s side that causes this. If it’s a confirmed issue it’ll be attributed an issue thread, otherwise not. For things like this though, they are a bit hard to pin down. If it’s not access issues much of the time the installation is corrupted but since you’d already tried reinstallation that’s not it. There’s not really a true time frame for this if a response comes.
Yeah been waiting for 7 days now and nothing this really sucks I wanted to start 2 weeks ago…
I understand the frustration! This issue is a tough one to diagnose as it’s likely a factor in the ecosystem. We can go over a couple of the more common issues that could cause something similar but these usually have far different symptoms.
Oftentimes during the first run of UE5 the User Access Control asks you to allow it through your firewall, if you had missed this before it may not ask again and you may need to put an entry into windows defender. Usual symptom: Unreal won’t even show the launching window just fails silently.
An old issue with some AMD based laptop drivers, you’d already updated your visual drivers are your other drivers up to date? If not: Usual symptom is crashing once the editor completes it’s opening or before it even shows the launcher image.
Have you ever changed the drive this launches from? Symlinks can really make a mess of accessing resources if you’d ever moved locations without the use of the editor. (No one does this but I would be remiss not to mention the possibility). Is this launching from your primary drive or on an external?
I tried the first 2, yes. About the 3rd I have it on my primary drive, and yes I think I have but I uninstalled the engine and then just reinstalled it to the other driver
If you completed the uninstallation through the launcher and the reinstallation at the new location that shouldn’t be the cause. I’m reading through the source code that’s run for those targeting packs to glean some insight, but since I’m more of a game developer than an engine programmer it’s a dense novel to say the least.
I’ve finally fixed it, I’m so happy. If anybody runs into this issue, this helped me: Unreal Engine Editor doesn't start, stays at 0% - Initializing - #15 by Uncljam