On each computer, open the Sage 50 file and select File, Properties.  See if each of the computers are using the exact same file.

If you are using version 2020.2 then select File, View All Users while you are all in the file and you will see everyone in the file.

My guess is that you are using two different *.sai files.

Thank you Richard!

That was very helpful and we have since fixed the problem. For some reason only two of our three users can be logged in at the same time in order for data entries to be saved properly.

Thank you Richard!

That was very helpful and we have since fixed the problem. For some reason only two of our three users can be logged in at the same time in order for data entries to be saved properly.

I am not fully sure I understand what happened.  Were you using two different *.sai files?

Premium 2-user versions can be installed on two computers and only allow 2 users to simultaneously work on a file.  If you have a second Premium 2-user program, then you will be allowed to have up to 4 computers installed with the program and up to 4 simultaneous users in the file.  Each 2-user version of the program will have different serial numbers and keycodes unless you specifically purchased the 4-user licenses from Sage.