Maintenance for the week of December 8:
• [COMPLETE] ESO Store and Account System for maintenance – December 10, 9:00AM EST (14:00 UTC) - 12:00PM EST (17:00 UTC)
The list that I've been referencing is this one. The author has been doing a good job of keeping it up to date.
In general, if a set has no condition (other than the number of set pieces) associated with it, it will always work. If it does have a condition, then you'll need to look at the list I sent above or the original patch notes.