This shouldn't be legal. The software was clearly marketed as a classic fixed-in-time release, like the old CD releases, that would not be updated but would work indefinitely. Now they're going to boldly revoke the licenses???
After all, a computer with the date set to 2021 will still function...
They were selling it until October 2021, so it's not some ancient system. By building a time bomb into it, they misrepresented what was effectively a $50/year subscription as if it were a $229 purchase. Should be a slam dunk case, but it won't be.
They sold a perpetual product that broke in sync for every user, and the reason it is breaking is because of a license checking feature.
Not an easy case, but it could be argued they advertised a product as perpetual while it's effectively an X years license.
The fact that the breakage is related to the license might be relevant, you can stop supporting license checks, but do it to the benefit of users, not conveniently to their detriment as an upsale mechanism