can't place doors since the new Cottage Living pack

It is always necessary to make sure that all of your gameplay mods have either been updated or given the all-clear after every patch -- some patches just hit some mods harder than others do. This particular patch broke almost every gameplay mod, so odds are that the vast majority of them need to be updated, but also with this patch a few specific mods were affected in a way that makes various types of content, even EA objects of that type, disappear if you try to play the game without updating them -- doors, computers, sinks, counters, etc. (Past patches have done the same for other things too, like sofas and beds.) Make sure ALL mods that change game behavior or add brand new gameplay get updated (unless you go to check them for an update and instead find that the creator has stated they don't need one), and you'll be fine.

However, if you saved the game while your doors were missing, then you'll also need to roll back that specific save or saves to a time before the doors disappeared, otherwise they will NOT come back. If you exited WITHOUT saving when you noticed the missing doors, they'll come back on their own when your mods are up to date.