If a FileMaker Database is just copied into the server folder for hosting, due to the various permissions that FileMaker Server requires to be set in a hosted database, most times the database will be served, but the database will be locked.
You need to make use of the 'Upload a Database' option in server, which correctly sets the permissions and allows you to open the file with full read/write privileges.
This happened to me today - I absent-mindedly dragged the updated database into the server folder and we couldn't modify it. I realised immediately what I had done, so closed the file in the server, dragged it back out of the folder to the desktop and then used 'Upload a Database' to put it back. Fixed!
Best wishes - Alan Stirling, London UK.