You might try upgrading to the latest 8.1.x version.
8.1.5 contained a fix for an issue that sounds similar:
Fixed a bug that caused tags to get stuck with Bad_NotConnected or Uncertain_InitialValue quality on startup or reconnect.
I don't know for certain whether that affected 8.0.x versions or not.
However if the problem is just that the device isn't responding, which your original post with the timeout issue is showing, then you just have something misconfigured either in Ignition or on the PLC side.