Azure & HyperDB

I’m experiencing odd behavior. I have two wordpress front ends running as web apps in Azure, one in the West and one in the East. I’ve added HyperDB to both, configured with a master and one slave. It works fine on the East server but on the West server it takes me to the WordPress install page as if I don’t have a wp-config.php. I’ve quintuple checked that it is there and matches the settings on the East server. Any idea what would cause it to disregard the wp-config and try to install? I’ve tried using php 5.4 and php 5.6, same result.

https://ww.wp.xz.cn/plugins/hyperdb/