pager is not working on update of Views 7.x-3.7 to Views 7.x-3.8
I recently had the same problem. Issue for me was Views 7.x-3.8 changes the file plugins/views_plugin_query_default.inc to move the following code from the execute function to the query function.

I fixed it using the following patch:

https://www.drupal.org/node/2276165