Squid + HTTP Error 417 Solution

[Stewart]

We've had trouble with Squid interfering with communications with different vendors (HH2, Labtech, etc.) that would produce an HTTP 417 error and had difficulty finding the appropriate resolution so I thought I would post it here.

Navigate to Services -> Proxy Server
In the "Custom Options" field add "ignore_expect_100 on" (without quotes).
Save and restart.

It's worked for us and I hope it helps someone else along the way.