There have been changes to the licensing for the Tag Historian as of RC2 that will be in effect for 8.1.0. A Tag Historian license is now required for storing or querying history via Ignition or any 3rd party modules that use the Tag Historian APIs.
Can you please confirm that both systems you are using for Tag History (central system and the remote system) have a licensed Tag Historian module or have the Tag Historian module in a Trial mode?
Thanks,
Garth