The custom DR dll that has been built and deployed works correctly with PI System Explorer but not with PI ProcessBook. The custom DR dll is deployed when the client opens PI System Explorer and navigates to the attribute that is configured to use the custom DR. The dll is automatically downloaded from the AF Server to c:\programData\OSIsoft\AF\PlugIns\220.127.116.11\4.0 as expected. When I attempt to access this attribute with PI ProcessBook I do not get any data. I'm wondering if ProcessBook is looking for the custom DR dll in a different folder that the AF folder that it was automatically downloaded to?