I have just downloaded mod_questionnaire_moodle23_2012082000.zip and unzipped it into my module directory, visited the Admin pages in Moodle and nothing happened. The upgrade is not happening. I have turned on Moodle debugging and still get no errors. The upgrade just is not occurring.
Our database was upgraded from 1.8 -> 1.9 -> 2.0 -> 2.1 -> 2.2 -> 2.3. I have updated the schema to be the same as a brand new install of Moodle. When I did the upgrades I installed the appropriate questionnaire plugin at each level before moving to the next version.