I've just upgraded a test site from 4.7.15 to 4.7.21 on Drupal before going live. The System Status page isn't showing as expected and the console has this log:
GET failed for ..../sites/mysite/files/civicrm/persist/contribute/dyn/angular-modules.33b51763aa1098ba_etc_etc.js
This file doesn't exist. Note the Drupal site is not in sites/default/ but I have set the Civi Resource URLs correctly (hopefully) and cleared the Drupal and Civi caches. Any suggestions?
I've previously (and now) done some messy tweaking of $filesURL in CRM_Utils_System_Base to cope with not being in "default".