If you're a new player trying to play the free to play version of eternal crusade here is a work around as found on the steam forums.

"paste this into your steam browser (or paste it in a steam chat and click the URL)

steam://run/375230"

this should install eternal crusade as the F2P version and allow you to launch it as normal once installed.

Edit. It would seem using this method to access f2p breaks the transition to a premium account if you wish to upgrade. To get around this you must first uninstall. Max on discord discovered this and found to transition to squadron edition he had to " go into steam support and "permanently remove this game from my account to get rid of the F2P version... now i can buy squadron edition"

A big thank you to Urtuah-Jibblies and Max for this information this thread will be locked and pinned.