How do I get my dlcs back?

[Yog-Sothoth]

I had to uninstall and reinstall and now all my DLCs are gone.

[Desert Orchid 1]

There are a few in-game bugs that restrict a player from downloading their content. These instructions are meant to help PC players manually install their authorized DLC. Downloadable content can be manually installed in the PC version of Dragon Age: Origins. However, some downloadable content, such as Warden's Keep, requires authorization. As such, they cannot be enabled in-game until they have been authorized—either by entering a promotional code or by purchasing the content.

To install downloadable content manually follow these instructions:

Download the DAZIP file.
Locate daupdater.exe in your game folder. For example, Steam users will find the file at: C:\Program Files (x86)\Steam\steamapps\common\dragon age origins\bin_ship\. Users of the Ultimate Edition will find the file at: C:\Program Files (x86)\Steam\steamapps\common\Dragon Age Ultimate Edition\bin_ship\. Otherwise, the default location is at C:\Program Files (x86)\Dragon Age\bin_ship.
Run daupdater.exe
Click Load DAZIPs and browse to the location where you downloaded your DLC .dazip file.
Install it.
Run Dragon Age: Origins and check your DLC
Note: You might want to change the .zip into .dazip if you find daupdater can't see the zip files.

Be aware that a majority of the DLC requires an active internet connection and also requires you to be logged into your Bioware/EA Online account that you used to purchase or redeem the content. Otherwise you will get Unauthorized info in the Installed Content.

Make sure the offer file is really installed, by looking in C:\Users\%username%\Documents\BioWare\Dragon Age\AddIns, there should be a folder of the same name. If it is not there, unpack it from the dazip file (from inside Contents\Offers). It might also help to put the manifest.xml file from the dazip to its respective folder within AddIns for main file and Offer folder for offer files).

[Katsu]

Sorry for the necro bump.
Just in case, this is also for those having the issue and find themselves here in this post.
Had the same issue recently but found out the solution from Merek in his Merek's Modding Guide for Dragon Age: Origins.
All you have to do is run the DAOU_UpdateAddinsXML_Steam.exe found inside your "redist" folder from the game's directory.

Hope this helps. ;)