This is most likely caused by a corrupt preferences file.

The location of this file is:
~/Library/Preferences/com.vernier.loggerpro.plist

Follow these steps to reset the preferences file:

1. Quit Logger Pro.

2. Go to Finder and open the Go menu.

3. While holding the Option key, choose Library from the Go menu.
(Note: Library does not show up in the Go menu unless you are holding down the Option key.)
1848-Go_and_Menubar.png

4. Open the Preferences folder.
1848-Preferences.png

5. Search the folder for “vernier” to find the com.vernier.loggerpro.plist file. Move or copy the file to your desktop (as a backup).
1848-Searching_Preferences.png

6. If the file still exists in your Preferences folder, move it to the trash.

7. Restart your Mac.

8. Launch Logger Pro.

Published: October 11, 2019.