There are several things to check and several things that could be wrong. I would start by making sure that you have your ranges of IP addresses right and that you didn’t mistype any numbers.
Check your exclusions and be sure that your new ranges don’t fall in between the old ranges that were there before if you had any for the last set.
You can also check the workstations that didn’t take the changes individually. Be sure that they don’t have static IP address set for those computers. If they do, then change them to dynamic and restart the computers. If they have the dynamic bullet check then open up a command prompt and ping the server. If you get no response use the ipconfig commands. Release the IP addresses with the IP release command and then use the ip renew command.
If the workstations still do not work after trying the previous suggestions you can always assign your workstations using static IP addressing. It will be time consuming but with only twenty five workstations it shouldn’t be too overwhelming.
If the first suggestions do not work and you simply don’t want to do all the work of using static ip addresses then you can always start over and try putting in the new configurations again. The second time around be sure to restart your server and restart all of your workstations so the new changes will take effect. You may have to do it at a time when the company can afford the network to be all the way down for a few hours.