Why MAC time machine is working before, but doesn't work anymore after NAS or MAC been updated?
Due to MAC'time machine version udpated, some user couldn't get time machine work, thus need establish AFP connection before Time machine, please try with following action steps:
1. Establish an AFP connection to NAS (If NAS IP at 192.168.1.100), ex: Select Go > Connect To, and enter a afp://NASIP address > afp://192.168.1.100 > key in your NAS user'account & password.
2. Check the Time machine connection again.