WordPress provides an upgrade feature that makes it point and click easy to upgrade themes, and plugins. For years, this has never worked for me. Anytime I click the “update” button, I get the FTP login tab. I enter my credentials and then I get a blank page in the right pane. No error message. No error logged. This broken feature didn’t bother me much because it’s pretty easy to update the plugins manually. But it was annoying.
Today I installed another WP blog for a client and decided I really ought to make this work. I double checked permissions, and then noticed that even after providing credentials, I wasn’t seeing a FTP connection arrive when I attempted an upgrade. It was then that I had my ‘duh’ moment. I have a minimal PHP install, with only required plugins. I installed the FTP plugin for PHP and voila, plugin and template install/updates work.
If you are getting a blank page when upgrading a wordpress plugin, verify that PHP’s FTP module is installed and active.