The most common reasons for communications to work on the development PC but not on the PanelView hardware terminal is that the "Design (Local)" and "Runtime (Target)" communications configurations are not the same.
In the RSLinx Enterprise Communications Configuration, check to be sure that the Shortcut is configured to point to the same PLC in the Design tab as it is in the Runtime tab.
There is even a "Copy from Design to Runtime" button at the top of that screen to make this easy.
Also, when you download to the PanelView Plus using the Transfer Utility, make sure that the "Run Application at Startup" and "Replace Communications" checkboxes are checked. This assures that the PV+ terminal will use the newest communications configuration that has been included in the *.MER runtime file.