All of the following criteria must be met

• All Requirements must be installed.
• Full Latest.log file included. If no file exists then leave this unchecked and state so.

All of the following are optional to answer

• Tried reinstalling the Game.
• Tried reinstalling MelonLoader.
• Tried restarting PC.
• Was able to see the Start Screen.

Describe the issue.

I am currently trying to get MelonLoader working with a mono game using Unity version 2019.4.21f1 working under Proton. The game is 20 Minutes Till Dawn. I am having similar issues with all of the other Unity mono games I try.

I am presented with an error and a matching line in my log file: [INTERNAL FAILURE] Failed to Open Mono Assembly!

I followed the steps on the wiki for proton/wine installs and get a console window to appear, and I have enabled debug logs.

Here is my Latest.log.

Did you attach your log file?

• Yes, I attached my log file to the text box above.
• No, I could not find a log file at {Game_Directory}\MelonLoader\Latest.log

I indeed confirmed this is the case. When using a fresh prefix, CLR.dll fails to be found by .NET programs like dnSpy (e.g. when trying to attach a debugger). After running any --force dotnetXX command, mscoree.dll is not re-created (dotnet didn't get installed because we skipped it since it won't function) so the program then can't find mscoree.dll.

This is a complex issue, and, I'm not sure the real cause or solution or what's changed to create this problem in the first place ☹️

This issue is very likely related to improper dotnet config. For example, mscoree.dll is deleted when running --force dotnet472 as the wiki suggests to do, which of course is required for MelonLoader to function, however wine's installer explicitly removes mscoree.dll. Perhaps installing a different compatible dotnet version after cancelling the installer may fix this issue.

你可以看一下你是否使用了 ASCII 字符集以外的字符（比如汉字“开”）
You can check whether you use characters other than ASCII character set (such as Chinese character "开")

Aside from the start screen failing, i am still entirely unable to reproduce this issue
As i've mentioned before, you can skip vcrun2019/dotnet472 and see if that resolves your issue? I've already submitted a pull request to the Wiki here

Hi there, I can not reproduce this.

I need to update the Wiki entry anyways, vcrun and dotnet are just not required for ML to run anymore

Hi there, I can not reproduce this.

I need to update the Wiki entry anyways, vcrun and dotnet are just not required for ML to run anymore

Is this screenshot under Proton?

Based on your logs, the game's Unity version is now newer. The issue seemed to be specific to Unity version 2019.4.21f1 and possibly others. Whereas the game's Unity version in the screenshot you posted is 2019.4.40f1. It's only a minor version difference, but I could previously confirm that the issue occurred under Proton Experimental with a fresh Unity project I compiled myself using specifically Unity version 2019.4.21f1.

I really doubt that's a thing, but i'll install 2019.4.21f1 and make a demo project to test.

@Hexcede Was this resolved?

@Hexcede Was this resolved?

I apologize, I've been super busy so I haven't had a chance to test/respond. I'll go ahead and test and follow up later today.