You can try to reset/tweak server preferences.
Stop the server / fmsadmin
Go to: /Library/FileMaker Server/Admin/conf
\Program Files\FileMaker\FileMaker Server\Admin\conf
Backup and try to remove server_config.xml
Restart the server (this will dump the password, groups and schedules)
If it does not work, I would try to clear preferences on one of the clients and see if it helps.
There is no need for anything that destructive normally. If you completely stop FMS and all of its components, then change the IP address in the OS and then fire FMS back up it will use the new IP address. You will have to run the deployment wizard again if you have used an IP address instead of a DNS name to point to your web server, but that's just for web publishing.
This worked. Thanks for the help. Sue