Time Machine troubleshooting
Trying to start a backup and Time Machine...get a message that ( The disk image"IMAC-1C845E. Sparsebundle" is in use. Try ejecting the disc image. I cannot locate the disc image to eject
The External Hard Disk should be connected directly to the iMac and not through the router. If you want to connect it to the router, you can but you will need to learn how to use the router's connection. You will need support from your router company in order to do that. However if it were me, I would just connect the External Hard Disk directly to the iMac.