I had this issue in the past, and I can't quite remember how to exactly fix this issue.
I downloaded the test server once again, and I had the old files from:

http://wdl.square-enix.com/ffxi/preview/US/FFXITC.zip
http://wdl.square-enix.com/ffxi/preview/US/FFXITC2.zip
http://wdl.square-enix.com/ffxi/preview/US/FFXITC3.zip

They were still in my C:\Program Files\PlayOnline\SquareEnix\FINAL FANTASY XI Test Client folders.

How can I fix this issue?