The MsgBus Cert Updater package is not included in the Agent package 5.0.1 (and later). The package must be installed separately. It's available to download from the ePO Software Manager. You can deploy the MsgBus cert updater package to client systems through an update task in ePO. Select the MsgBus Cert Updater 5.x.x or later version option from the "Patches and Service Packs" section.

Make sure that the MsgBus Cert Updater package is checked in to the appropriate repository branch (Current, Previous, or Evaluation). The repository is the one from which your endpoints are configured to pull agent updates.