Are you using server or Filemaker to host your database?
What do exactly do you mean by "My old computer is still the host"?
When you say "host" do you mean you're hosting on FMS?
Sorry for any mistakes, I am not too familiar with how this program works!
The database file that everyone works off of is on my computer. So for instance if my computer is off, they cannot open the file. It was on my desktop. Now that I've transferred everything to my new computer, the database does not update with other peoples changes. If the problem is that they need to open their file from my new computer, all changes made recently are lost.
FileMaker Pro or FileMaker Server should be installed on the new machine and used to open this database file.
They then should use Open Remote to find and access this database file. You should do the same from your older computer.