I'm trying to test the workflow functionality in Alfresco 4.2 Community, so I created some user accounts and sites. I logged in to a few of them and created some sites and content. For now I just wanted something simple to test workflows, I upload a document and send it to an user for review. When I try to use one of the default workflows that seems to fit that scenario I can't find my users in the select users dialog. I can find some the already existing users (Alice Beecher, Guest, Admin, Mike Jackson).
I also tried searching for them through the People search, but they are not visible there either. I've logged in and joined a test site with some of the users, and have tried to create the workflow from inside and outside the test site. Is there something that I have to enable on the users for them to be visible on searches and when creating workflows?
Try rebuilding your search index. If you are using SOLR (the default if you installed 4.x from the binary installer) you can rebuild your index as described in this link.
If you are using Lucene (the default if you installed manually by deploying the alfresco and share WARs) then shutdown the server, edit alfresco-global.properties, and set index.recovery.mode=FULL. Now restart the server and wait for the index to rebuild. After restarting, don't forget to remove the index.recovery.mode setting or change it to AUTO.