Why are all resources in the cluster in Stopped state when fence_scsi or fence_mpath is configured?

Issue

• All cluster resources appear in state Stopped, and it's not possible to start them up with pcs resource enable.
• It's not possible to start resources or to move them between nodes. Restarting the cluster does not help.
• Unfencing failed using a fence_scsi or fence_mpath device. Messages like the following are seen in the logs:

fvm-rhel-7-5-95 fence_mpath: Failed: device " /dev/mapper/mpathb" does not exist
fvm-rhel-7-5-95 fence_mpath: Failed: device " /dev/mapper/mpathb" does not exist
fvm-rhel-7-5-95 fence_mpath: Please use '-h' for usage
fvm-rhel-7-5-95 fence_mpath: Please use '-h' for usage
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [ WARNING:root:Parse error: Ignoring unknown option 'port=fvm-rhel-7-5-95' ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [  ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [ ERROR:root:Failed: device " /dev/mapper/mpathb" does not exist ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [  ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [ Failed: device " /dev/mapper/mpathb" does not exist ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [  ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [ ERROR:root:Please use '-h' for usage ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [  ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [ Please use '-h' for usage ]
fvm-rhel-7-5-95 stonith-ng[9466]: warning: fence_mpath[19896] stderr: [  ]

# # # OR # # #

Jun 25 08:54:37 node42 fence_mpath: Failed: device "" does not exist
Jun 25 08:54:37 node42 fence_mpath: Please use '-h' for usage
Jun 25 08:54:37 node42 stonith-ng[59191]:  notice: fence_mpath_on_1:70499:stderr [ 2020-06-25 08:54:37,341 ERROR: Failed: device "" does not exist ]
Jun 25 08:54:37 node42 stonith-ng[59191]:  notice: fence_mpath_on_1:70499:stderr [  ]