1. See network status on your wallet on bottom right. The button should be Green Circle, otherwise there's problem with your connection (or the server/nodes problem).
2. Make sure any firewall on your Mac don't block Electrum.
3. Try to select the server/nodes manually (https://1209k.com/bitcoin-eye/ele.php)
4. Click 'View' --> 'Show Addresses' and see if the receiving address is available there.