Rockwell Software "Studio 5000" users have reported issues getting InteractX and Xpress (ControlLogix Driver) to connect and download tags from the PLC even though they are able to PING the PLC from the HMI.
After investigating the various users configuration we found that it was only in newer firmware versions.
The common link between the problem applications were using the "Studio 5000" software and the lowest firmware revision on the PLCs was version 19.
We found a document on the Rockwell Automation website that is linked below.
Once you have downloaded the programming manual, open it and go to page 63 "Data access control"
On Page 63 of the "Logix 5000 Controllers I/O and Tag Data Programming Manual" it indicates that starting with version 18 and later of the Logix Designer Application, there are two new tag attributes.
External Access and Constant.
It is the External Access setting that is preventing the HMI from downloading the tags from the processor and referencing tags directly. Apparently, the default setting is to "Block" external access to the tags. It is necessary to set the PLC tag properties to allow reading and writing in "Studio 5000" and once this is done, all of the tags you expose will download into the ControlLogix Comm Servers in InteractX and Xpress.
The Rockwell manual gives detailed steps to setting the tag properties.