Trying to connect gives this result:

Aug 22 19:27:57 memoryalpha ModemManager[4889]: <info>  [modem0] simple connect started...
Aug 22 19:27:57 memoryalpha ModemManager[4889]: <info>  [modem0] simple connect state (3/10): enable
Aug 22 19:27:57 memoryalpha ModemManager[4889]: <info>  [modem0] state changed (disabled -> enabling)
Aug 22 19:27:57 memoryalpha ModemManager[4889]: <warn>  [modem0] OperationNotAllowed
Aug 22 19:27:57 memoryalpha ModemManager[4889]: <warn>  [modem0] OperationNotAllowed
Aug 22 19:27:57 memoryalpha ModemManager[4889]: <warn>  [modem0] couldn't enable interface: 'Invalid transition'
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <info>  [modem0] state changed (enabling -> disabled)
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <info>  [modem0] simple connect started...
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <info>  [modem0] simple connect state (3/10): enable
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <info>  [modem0] state changed (disabled -> enabling)
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <warn>  [modem0] OperationNotAllowed
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <warn>  [modem0] OperationNotAllowed
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <warn>  [modem0] couldn't enable interface: 'Invalid transition'
Aug 22 19:27:58 memoryalpha ModemManager[4889]: <info>  [modem0] state changed (enabling -> disabled)