I clicked on the Bitcoin Core symbol on my desktop computer to open it and I got an error.  I think it said something about application failure and asked if I wanted to ignore it so I said yes (was that the wrong answer?).  Then Bitcoin Core came up but now says "No block source Available" and shows zero Bitcoin in my wallet.  It loaded almost instantly but says 6 years and 20 weeks behind.  It shows former transactions in a grayed out box as well as previous wallet addresses I've used.  I've tried to start over by downloading Bitcoin Core again, but the same thing keeps coming up..."No Block Source Available."

Can anyone help me with this?  At a loss.  Thank you!!!