Was the subscription for that Montana or another GPS? Relevant info is here https://buy.garmin.com/en-US/digital/maps/on-the-trail-maps/birdseye/birdseye-satellite-imagery/prod70144.html, look at the requirements tab.
My Subscription to Birdseye Imagery ran out but I still have the imagery I downloaded on my computer and can view it in Basecamp, but when I try to copy the Birdseye Imagery to my Montana 650 I get an error saying "The device Montana 650 does not have an active BirdsEye Imagery Subscription". I was under the impression once you downloaded BirdsEye data you could use it forever.
On a slightly related note, it's unfortunate that Garmin doesn't provide any details as to the age of the imagery available. If they did, more people would presumably update and maintain more active BirdsEye subscriptions. (Instead of making due with the older imagery.) ~ I'm still using the 2 year old imagery (downloaded 2 years ago) on my Montana, but would have considered upgrading if I new there were updated aerial images for the region....
Out in the middle of nowhere (so I thought) the other day: I ended up in someones back yard. ~ My local BirdsEye imagery is apparently way outdated, even older than I thought..... It was quite obvious that this housing development I brushed up against had been expanded quite a few years ago.....
Please read about BirdsEye map limitations and archiving techniques starting here. ;-)
It is common knowledge that most BirdsEye imagery is more than a decade old, and nearly useless for that very reason.