I’m using Katalon Studio versions 6.1.5 and 6.2.1 on Windows 7 and found the same problem in both versions.
If the proxy is configured as “Use system proxy configuration” whenever I lunch a test case (or suite) it takes several long minutes before the test starts. After this delay everything works ok, I mean Katalon Studio seems to be using the system proxy configuration and has no problem to reach URLs through the proxy.
To solve it I just configure the proxy at Window->Katalon Studio Preferences->Katalon->Proxy as “Manual Proxy configuration” and the delay disappears.
However, if I configure the proxy as “Manual Proxy configuration” from the product activation dialog, this workaround doesn’t work
The delay happens even when there is no need to use the proxy because all the URLs are from the Intranet.