Dropbox won't connect

After updating Mojave to 10.14.4 on iMac, (from whatever the previous version was), Dropbox no longer can connect. Reinstalling Dropbox and restarting the iMac (a few times) has not helped. Dropbox support has not helped.

It acts like an anti-virus or proxy or firewall issue, but I don't have any anti-virus software, am not running a proxy or VPN, and am not behind a firewall. All I did was update Mojave.

Any ideas? Thanks