Interface 'Psr\Http\Client\ClientInterface' not found even after using composer dump-autoload

[hdevacc]

Someone seem to have messed composer in the project, and now after I ran composer dump-autoload the app was broken.

This is a legacy internal app with no access to the internet anymore so I can't copy files into it.

Now I get the following error:

Interface 'Psr\Http\Client\ClientInterface' not found at
C:\project\vendor\guzzlehttp\guzzle\src\Client.php

What I know is that all the right files do exist and that this package does work, because whenever I copy the backup vendor folder it working again.

I also have the "guzzlehttp/guzzle: "^7.2" in the require key of composer.json

Although when I run composer dump-autoload it does not show guzzlehttp in the list of Discovered packages (but I'm not sure it's supposed to show it? If yes then it could be related to the problem)

How can I manually fix it without internet connection?

Is it purely composer related error and I can try to fix it by editing files in the vendor/composer folder? Or I would also need to add some code to the Laravel project itself maybe somewhere in the config files?