masternode.conf hasn't been used for almost a year, which instructions are you reading?
The problem in this error message is that dashd is apparently not running, or the port to connect to dashd is blocked. The first thing we need to do is check if it is running, and if it is not running, find out why not. Type: "pidof dashd". If you see a number returned, then dashd is running and you should check if your firewall is blocking ports.
If nothing is returned, it is not running. You can try to start it by typing "~/.dashcore/dashd". Then wait ~30 seconds and type "pidof dashd" again to see if it is running now. If it is, try sentinel again. If not, you need to find out why it is shutting down. Check your debug log by typing: "tail ~/.dashcore/debug.log". This file should contain error messages describing any incorrect configuration settings you may have.
In general, you cannot start a masternode or test sentinel without having a 1000 Dash UTXO. If you want to practice without this, you should try and use testnet. Instructions are here:
https://docs.dash.org/en/stable/developers/testnet.html
