After updating to Yosemite, some users are being prompted to grant access to TextExpander Helper in the Security & Privacy preferences of System Preferences, and they're finding TextExpander Helper isn't in the Accessibility list under the Privacy tab. This appears to be a bug in Yosemite's accessibility access preferences, and it affects other apps with helpers, such as Keyboard Maestro and Witch.
The workaround is to drag the TextExpander Helper app directly into the Accessibility list by following these instructions:
It's possible that TextExpander Helper will not appear in the list after you've dragged it in, but behind the scenes your action has granted the permission to TextExpander Helper that it needs. Hopefully, OS X will return to displaying helper apps in a future update.
If you are one of the few cases where this doesn't work, we recommended rebuilding your Launch Services database using a tool such as Cocktail and restarting your Mac.
If, after following these steps, you still encounter trouble, please get in touch with our support team.