You must be quite frustrated when you encounter time machine could not be accessed error -1. Time machine is an inbuilt utility that provides backe up of data when it is lost from the Mac system. You have to first set up the time machine then every changes that you make on the Mac hard drive is saved in the external drive called Time capsule. So you can restore the files in case of data loss from the Mac drive but what if you get time machine could not be accessed error -1. You will not be able to restore any data back so you have to either fix it or find another solution to restore you data. The error may cause when the time machine is not properly connected with the system. So try to reconnect it and complete the backup issue. IF the time machine could not be accessed error -1 is still there then you have consult a professional in the meanwhile you can restore the data using Mac data recovery software. It will scan the Mac drive and then bring out deleted data in the preview, just select them to restore.