I'm having the same problem. One of my sites was on a fairly old version (5.4.2.2 maybe?). The automatic update would not work.

I have now updated each incremental version manually. After each update, I have tried the automatic update from the control panel. Nothing happens, I just get a blank screen forever.

Even now, at 5.5.2, I cannot perform the built in upgrade to 5.5.2.1.

I might try manually creating the "updates" directory, but why can't the stupid script do this?

I have been using C5 for some years and it has many great features, but they often seem to fall down on the simplest things like this... very frustrating!

To go around the problem. I manually uploaded 5.5.2.1 to the update directory. once that was completed the dashboard was able to find it and install it.

The part that is missing from the script is error message handling. it should be able to give a message when it fails so we can tell what to do instead of hit and miss

Forget about the "updates" directory idea... It's already exists.

I wonder if the problem does not relate to that directory, however. I have another installation that is updating from the dashboard with no problem, but it DOES have all the different older version directories in the upgrades directory.

Unfortunately I don't have time or internet speed to experiment with uploading all the old versions to this installation to see if it will fix the problem :(

It is very important to note that you need at least 5.4.2.2 to be able to upgrade to 5.5.2.1, So double check before trying..
To get a successful upgrade you should download the latest version from the concrete website (currently 5.5.2.1)
Unzip the package and manually ftp it to your root/updates/ folder
then run this script from your web browser:
http://www.yoursite.com/index.php/tools/required/upgrade......

If you already have an installation of concrete5.5.2.1 and you want to re-install it, then run this script from your web browser:
http://www.yoursite.com/index.php/tools/required/upgrade?force=1......

In both cases replace yoursite.com with your domain name..