Are the ip address' on the same subnet?
Could it be that you missed a file reference?
I am still not sure why it is now working, but it is! Partially this is because of the limitations I have on testing. I am a team of one when I develop this software, and licensing and financial limitations mean I can't readily test databases running on the IP, I have had to resort to using my IPAD and testing by borrowing a neighbors wifi in order to make the connection. So, I rely on my client to test, and I can't always be looking over their shoulder to see what issues might be causing the problem.
I do know that I checked all of the configurations under manage external data sources before I retested and reset them. (Which incidentally IS also the place that you can eliminate annoying references to secondary attached databases once you are quite done with reorganizing your tables when you split a database...nice to know!)
The great virtue in splitting the database, for me, as ongoing developer and person responsible for maintaining data integrity and solving issues when under development, is that I was able to finally create a "clean" relationship chart out of a developmental sandbox. Oh Joy! The time spent on this effort will reap great dividends for both myself and my clients!
I would happily try to help others who decide to undertake creating a split database solution, and would love to hear from others who have successfully done so...I imagine there are issues I haven't yet addressed, and working as a "solitaire" has me missing the other programmer at the next desk. Oftentimes, just the opportunity to "share" a conundrum helps to clarify a murky situation.
You don't tell if you are hosting the database on FM server or use FMP to host the files.
Are you sure that the second file is also set to sharing? and if you use FMP are you sure that the second file is also open on the server?
Then you should be able to connect to the second file.