There are two possibilities:

1. The HotSync conduit is not installed on your computer. Check for the conduit:
In Windows, click on the HotSync icon in the System Task Bar and choose Custom… from the menu.
In Macintosh, start the Palm Desktop, select the HotSync menu, and choose Setup.
If you do not see Data Pro listed under Conduit, install Data Pro from the CD.

2. Upgrade Logger Pro. If after completing the HotSync, you move the mouse into and out of the tool bar and your data appears, this is a known bug in Logger Pro 3.1 that is fixed in all subsequent releases. You may download a free upgrade from our website at https://www.vernier.com/tech/lpupdates.html

3. On Macintosh computers only, this is a bug in the conduit. A workaround is to delete this file:
users:(user name):Library:Preferences:DataPro Conduit Preferences
This file keeps track of the last HotSync’ed username. When a username with fewer characters is HotSync’ed after a username with more characters, the last characters of the longer username remain. The conduit cannot find the corrupted username’s Data Pro folder into which to write the uploaded data file.