You'll need to tell us exactly what you have at this point. How are your files hosted?
They are hosted on a server
What kind of server? on your local network for from a hosting service?
What version of FileMaker Server is hosting the files?
Are they hosted by Filemaker Server, Filemaker Pro or just stored in a shared directory on the server?
it is on a 3rd party server. All the other computers on the network are working, it is just the new one that will not connect. Filemaker Pro 9. It is just stored on the server.
FileMaker database applications should only connect to hosted filemaker databases where the file has first been opened by either FileMaker PRo or FileMaker server installed on the server computer. Trying to directly open the file from a shared directory can damage the file.
If you have FileMaker 12, you will be unable to see or open hosted files hosted by earlier versions of Filemaker and Filemaker server and vice versa.
If by "3rd party server" you mean that you have contracted with another company to host the file for you, you should contact them for additional support in connecting to the file as they will know the details of how it has been hosted and how you should connect to it.
You'll need to first set up an external data source connection, even use the Remote button, to locate the files you want to open. On a new computer this may take a little effort.
If you have an opener file on another computer it may work on yours.
If you are trying to work with a local file you may have a broken TO, look in the Relationship Graph and a broken To will be obvious. Double click on it and reset the external connection.