Time Machine Back-up to separate drive
I have a G_technology G-Drive mini (9 years old) that I been using as a back-up drive for my MacBook Pro (Retina 15, mid-2015) running OS Mojave 10.14.6. All of a sudden Time Machine says the disk is read only and can't be repaired by OS. Disk First Aid doesn't work. Is this a hardware problem and I should just buy a new back-up drive or a software problem?
MacBook Pro 15″, macOS 10.14