Well you should try adding nodes manually, but i find it really weird that it suddenly stops working like that. You should check ports again if adding nodes manually does not work. You need to create bitcoin.conf on:
C:/Users/(username)/AppData/Roaming/Bitcoin
Here are few nodes that i have picked for you from the Bitcoin ABC list, no need to add alot of them because this amount will work just fine.
Insert the following into bitcoin.conf:
daemon=1
rcpallowip=127.0.0.1
rpcuser=x
rpcpassword=x
addnode=74.70.90.94:8344
addnode=101.201.40.27:8333
addnode=174.7.119.132:8333
addnode=91.108.41.131:8333
addnode=101.37.161.153:8333
After that, save the file (make sure that the file is bitcoin.conf, and not bitcoin.conf.txt as windows by default hides known file extensions)
That should work, but if it does not then you should probably go for full installation again.