There shouldn't be any problems connecting to the in-game library regardless if your online or offline.
Here's something to try to see if you can see your library.
1. From the Main Menu, go to Options (upper right corner) > Game Options > Other (Or press the F4 key)
2. Turn off (uncheck) Online Features Access and click Apply.
-- The library should be accessible.
3. Click the Open My Library button in the top right of the screen to see if it's accessible.
Online Features Access turned off means the gallery is turned off and you only have access to the library.
Accessing the in-game library should be possible regardless if you have online features on or off. You can still click the option in the upper right corner of the screen to get to the library.
In other words, you'll have in-game access to the files in your \Documents\Electronic Arts\The Sims 4\Tray which are families, houses, rooms and community lots.
Origin maybe saying something about that because there is an actual update to the Origin client. I just got into game and saw that Origin has a new update.