Version 3.1.3 is outdated.
Update to latest version, but only download electrum from the official site:
https://electrum.org.
If you see some message in your old version telling you to update via github, do NOT click on it.
There is a (not severe) vulnerability in the old versions which allow the remote server you are connected to, to display a custom message. This is a phishing message.
Download electrum from the official site and verify the signature to make sure you have the correct file.