[Plum]

I want to updgrade from 3.3 to 3.4 and after that to 4.0.
When I try to upgrade from 3.3 to 3.4 I get the following error in the first step:

Error: Could not load stylesheet stylesheet.css!

I already checked that the header.php is correctly transmitted, as mentioned in another post, but it still does not work.

[Steven]

In the first step of the installer? Check that this file exists:

/install/view/default/stylesheet/css/stylesheet.css

If it does, open /system/engine/base.php and find this line:

PHP Code:

<?php 

die('<b>Error</b>: Could not load stylesheet ' . strtolower($cmtx_stylesheet) . '!'); 

[Plum]

Okay, the stylesheet was really missing. But I don't know why 

Now I get an error in the second step, when I click "Click 'Start' to begin.":
Error: Could not load language main/system!

Info: I have already translated the 3.3 to german which I want to upgrade now.

[Steven]

I guess you're missing this file as well:
/install/view/default/language/english/main/system.php

[Plum]

Thank you for the help. It works now.
Somehow FileZilla seems to have problems uploading some of the files.