After not accessing my Bitcoin Wallet on a rarely used computer for a couple of years, I did so about a month ago. I received the subject message and that the synchronization with the network was 1 year and 48 weeks behind. I Googled and searched, tried many possible solutions; it actually started processing at one point, but quit after about a week's worth of transactions. Today I decided to reset Bitcoin Core and changed my router's security level to low. Port 8333 is forwarded to the IP address of that computer. Restarted and without changing anything, synchronization began. It's now down to 1 year 24 weeks behind with 8 nodes/services connected (first I've seen of any connections).
Well, big sigh of relief ... hoping this may be of assistance to someone else with this problem.
"Reset Bitcoin core"? What version were/are you running?