Custom fields of type select not displaying in Activity Report
This appears to be a regression in CiviCRM 4.6.32.  (It doesn't appear to affect CiviCRM 4.7.28.)

I have recreated this on the sandbox site.

I have raised this as a bug in the CiviCRM issue queue:

Custom fields of type select not displaying in Activity Report

UPDATE

It was subsequently raised as a bug by Martin Castle:

Custom data fails to pull through to reports 

And a fix has been released by VangelisP:

Resolves regression issue with non-dynamic custom fields

This will hopefully be included in a future release of CiviCRM 4.6