RDi drops connection

All,

If this is the wrong list, point me to the correct one.

Ten days ago we replace our Meraki firewalls with Sonicwalls. About the
same time, I replaced my desktop. Since that time, the RDi connection to
the IBM i will time out in a matter of minutes, like less than 30. My old
desktop is still up and running and the same thing happens to it. This is
irritating.

Since it is happening on both desktops and never happened with the old
desktop and old firewall, I'm speculating it's something on the new
Sonicwall firewalls. Note that our IBM i is in the cloud and we connect
via a site-to-site VPN. Though the RDi session times out, 5250 sessions
_never_ do.

Keepalive is enabled with:
Socket read timeout (ms) 3600000
Keepalive Response Timeout (ms) 60000

Suggestions? Should I change those numbers (but they're the same as
always)? What should I tell the firewall guru?

Thanks.