Bex report not getting data from Remote cube

Hi Experts,

Can you please tell me under what conditions a BW and R\3 Reconciliation report may not be able to fetch the data from a SAP Remote cube?

(Warning message: Unable to read data from Source System and remote cube)

Apart from the below conditions:

Source system connection-O.K

List cube shows data for Remote cube

Proper Remote cube selected in BEx Query.