Help! Is there some sort of trick to make the exhaust hose stay in place?

Despite my best efforts, it wants to slip out of place both on the back of
The portable AC unit as well as from the connector in the window.

What am I doing wrong? Any hints or tricks on how to make the connection,
Insertion, or whatever, will be greatly appreciated. Manufacturer's instructions basically say "connect exhaust hose".

If you go to the ducting section of your friendly local hardware store, they should have things that look like really big cable ties (aka zip ties). Find one that's appropriate for the size of duct that comes off the back of the AC unit, then buy two.

These zip ties are normally used to attach flexible ducting to rigid fittings. They should do a good job of fixing the exhaust hose to the back of the AC, and to the window panel. Make sure you pull them nice and tight when installing them.