The purge triggers as long as one person is on the server, not dependant on your clan members being on. Our bases are not in the starter no-purge area.
Purges cannot happen if all clan members are offline, but if you did have at least one member online and still did not get purged, then perhaps it is bugged.
From the wiki " The Purge will occur for whichever eligible player is chosen - whether they are logged in or not (again, dependent on the server settings)."
I have been playing since early access and am very familiar with the purge mechanics. To put this to rest, we have had clan members on every night during the window.