IMCE 6.27 Missing Buttons to Upload to Editor
The issue in this instance laid with Google Analytics and it's Event Tracking. A quick test is to turn on the Google Analytics Module, then try to use the IMCE upload buttons again. If they return, do the following: 


Re-enable Google Analytics Modules you'd previously turned off to test. 
Goto /admin/settings/googleanalytics
Open the collapsible menu option "Page Specific Tracking Settings" 
Add imce to that list Click Save
Configuration and test again.


Your IMCE should be working again without issue should the Google Analytics have caused your issue in the first place.