Answer
This commonly traces back to the login process making a very large number of small client-server round-trips, over 100 individual FETCH calls against dictionary/view-metadata tables, each taking roughly 50-150ms on its own. On a low-latency local network this goes unnoticed, but the cumulative delay from many small round-trips becomes dramatically more painful over higher-latency links to distant offices, which is exactly the symptom of login being fast in nearby offices but very slow in distant ones. To confirm this specific root cause on your own environment: hold Shift while opening the IEE client, then, while still holding Shift, double-click the resulting login pop-up dialog to reveal a hidden '(debug console)' option; click OK and log in normally with the debug console enabled, first confirming Framework mode is set and, under Tools > Options, setting visible rows and rows-in-buffer to unlimited. Reviewing the resulting debug console output for a large volume of repeated FETCH commands during login confirms this exact root cause. This was a known issue that IFS's own Product Development team was actively addressing via a binary patch.