Since you mentioned the full node and port 8333, I assume that you are talking about bitcoin core full node and not Electrum Personal server because 8333 is exposed by the full node connection, not by EPS.
- Make sure you are using Electrum Personal Server and that it is running using CLI
Make sure port 50002 is open. [/li]
- Delete cached cert file
- Check the settings of the config.ini file for Electrum Personal Server and bitcon.conf for Bitcoin Core
- Use local IP and port number 50002.
These steps should solve your problem, if not, paste the logs here.