I am using a mid 2011 iMac and have upgraded to Yosemite. Currently on 10.10.1. As soon as I upgraded I was unable to access my drive on my 2tb time capsule (old version) or use it for a time machine backup. The drive lists under devices and shows its name but I cannot access or mount the drive. Thinking the time capsule was too old I went and purchased a brand new Time Capsule AC. But alas I still have the same issue. I have been through all of the support stuff on apples website. I have done a hard reset, soft reset, every configuration I can think of. My network setup is as this. Internet from Fios to TC via ethernet. Wired from TC to iMac via ethernet. the TC provides DHCP and NAT via wired and wireless connections. I have the drive listed as shared. I dont know if this is a Yosemite issue or a TC issue or a set-up issue. I hope its just a set-up issue that can be fixed and I am just setting it up wrong. Any help would be great. Thank you in advance!