Problems with SanDisk ArmorLock external drive

My external drive is directly connected to my MacBook but at the moment doesn't seem to be performing backups. When I looked for information using the Disk Utilities menu, ArmorLock is shown, along with Time Machine; information with the ArmorLock icon says the last backup was about a month ago and that the next one will occur when the disk is connected—which it already is. How can I solve this issue ('m also planning to try support for ArmorLock)?