Blank page after login with Magento Connect Manager

[caryatnid]

Hi there, I'm completely stuck and really hope somebody here can help me.

I have an existing Magento website and want to use Magento Connect Manager, for the last while I had a 403 error when I tried to access it: I changed the file permissions and installed magento-cleanup.php and now I CAN login - however after login, I get a completely blank page - i.e. a totally empty file when I view the source.

Does anyone have any ideas? Extensive Googling shows that this seems to be quite common - but I can't find the solution.

I need to install the plugin in order to install a plugin: http://www.magentocommerce.com/magento-connect/invoice-pdf-generator.html - If I can't get the Magento Connect Manager working, would you advise a manual install (I have never done a manual install of a plugin and have read that it can be tricky). I really want this fixed asap!

Thanks in advance for any advice!

(Edited to correct typos)

[Conor_Tomkins]

A blank page usually indicates a PHP fatal error.

Try adding ini_set('display_errors', 1); to the top of your index.phtml

Navigate to your Magento Connect and let me know what error it throws up!

[caryatnid]

Thanks a mill for replying. I should have said that I already did that, in the folder 'downloader' - i.e. htdocs/downloader/index.php - and it makes no difference - i.e. I still see a blank page and I don't see any errors. (I just tried it again and it is still the same). When I put in the wrong login details the system knows that it is wrong - I get the blank page after I put in the correct login details.

[JLHC]

Do you see any errors at all in your error_log? 

As for the file permissions, it can be a little misleading as different servers have different requirements.

If the server is running SuPHP / SuExec, all files should be set to 644 and all directories to 755. Otherwise only some files should be set to 644/755 while others should be set to 666/777 as per Magento's official documentation. 

If you are not sure whether your server is running SuPHP / SuExec, it is better to confirm that first and adjust the file permissions accordingly. 

[chip13]

Hello, I have exactly the same blank page problem every time I do an update Magento. And I do not know how to solve it.

In the file "index.php" folder "downloader" I added the line:
ini_set ( 'display_errors', 1);

Then I have the following message:
Fatal error: Undefined class constant 'DEFAULT_SCONFIG_FILENAME' in /var/www/vhosts/MY-SITE/httpdocs/downloader/Maged/Connect.php on line 167

What it is, what should I do?

thank you in advance

[chip13]

Nobody idea to help me?

thank you in advance

[dfc_admin]

This is what worked for me. My index.php file in the downloads directory had permissions set to 666. Lowering that to 644 fixed the problem. No more 403 error while attempting to access Magento Connect.

[chip13]

Thank you for your help dfc.

My index.php file in the file directory was already 644. However I suddenly tried with another possible permissions. Unfortunately, my problem is still present.

[chip13]

Do you have another idea to solve my problem, please ?

Thank you in advance

[drillsar12]

I would go to System>Configuration>Advanced>System>Log

Set Enable Log to Yes

Also go to Developer under same Configuration

Debug Profiler set to Yes

Log Settings Enabled to yes

Than try and go to Magento Connect and see if there is any logs in your /var/logs directory