It sounds like your workstations are not all pointing to the same data. The way you can fix that is to first determine which computer is seeing the latest data. With the Reporter open, on each workstation check the Hours records and perhaps a recently added volunteer.
If you cannot get into the Reporter, you can check the file attributes on files inside data folders to find the most recent dates. Compare the file sizes also. Often the Hours.dbf file is a clue with the largest file being the most recent.
On the computer with the latest data, find out where the data folder is (on the server) by going to the Help menu | About the Volunteer Reporter.
If it's a mapped drive, find out what computer and folder it is mapped to: open My Computer | Tools menu | Map Network Drive.
Now you have the basic information to set up each workstation to point to the same data. On each workstation click on File | Select Data Set: