I've been trying to install Itch on my computer, but it prompts an error:

There was a problem during setup: Could not validate version 15.21.0 of butler

I tried manually installing Butler but that has not helped, nor trying to restart/reinstall the app, or using Admin privileges. And I do not have an antivirus, so I cannot whitelist this app. And even when attempting to do so on Windows, the app does not show on my list to whitelist.

For reference I am using Windows 11 pro. If more information is needed, I'll be glad to help

You have some security software on your computer, or there is something about your network, that is preventing the app from functioning as intended. Unfortunately, an individual’s computer and all the third party software they have installed on it varies so greatly that we are unable to provide any more help than that.

I tried manually installing Butler but that has not helped

There is no way to manually install butler in a way that can be used by the app. Installing butler manually is only for developers who wish to use the command line tool directly.

In order for the app to function it must complete its own setup process, and any other software on your computer that gets in the way of that will prevent the app from being fully installed.

Hope that helps