I have periodically used my time machine for years now. The last time I backed up was November 2017 and I started to try and back it up last night and it took ages to "prepare" and started to back up, but then kept failing. When I click the red (i) symbol on my TimeMachine it just says
Time Machine couldn't complete the back up.
There's no further answer as to why. I ran it a few times and noticed that it now says that the last successful backup was June 2015. So I don't know what happened to the other 2 years worth of backups. It was still saying last back up was November 2017 on previous failures yesterday.
How do I resolve this?