3370566 - Job SM:RCD_CHECK_UPDATES failed with error "An Error Occurred while Reading from PostBox" - SAP Solution Manager 7.2

Job SM:RCD_CHECK_UPDATES is failing with the following error message:

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Job started
Step 001 started (program RCSU_AUTO_NOTIFY_AND_DWLD, variant , user ID SM_DL_RCD)
Job SM:RCD_CHECK_UPDATES started
Step 1: Attempting to read the Notification XML from Post Box
Call to the postbox system. Method name: cl_csu_notification=>READ_FROM_POSTBOX
Step 1.1: An Error Occurred while Reading from PostBox.
An exception was raised
Job cancelled

SAP Solution Manager 7.2

SM:RCD_CHECK_UPDATES, SM_DL_RCD, RCSU_AUTO_NOTIFY_AND_DWLD, An Error Occurred while Reading from PostBox, READ_FROM_POSTBOX , KBA , SV-SMG-RCD , Rapid Content Delivery , Problem