Answer
Look for a separate, specific grant listed under 'Activities' within the user's Permission Set — visibility for an Object-Connected item, like a connected Change Request attachment shown on another screen, is controlled by its own distinct Activities-level grant, separate from the broader module-level access grants that already let the user navigate and use the base module's own features. Granting that specific Activities-level permission resolves visibility for the connected object without needing any additional module-wide access.