Please try add @ exception firewall list on port (8080) not programs (managerserver.exe). It happened to me once. Located at Advance Settings.
@CarettaFPS what port are you using if its not the default one ‘8080’?
In Lan there is no need for port forward. port forward only relevant when you try to access via public internet network (need external ip for it)
May I know what os device are you using to access the server?
Be sure to check there is no other software than managerserver.exe using the default port 8080
Upload the screenshot of the error or the part that you are stuck.