If you’re having trouble getting the WordPress app for iOS to show your posts (symptom: constant HTTP 500/internal configuration errors in the iOS app), you might need to increase the memory limit for WordPress. This is particularly true if you have JetPack installed. To do that, modify your wp_config.php file (which lives in your /wordpress directory).
That worked for me, so now I can post this from my iPad!
Hat tip: WordPress Support forum post