I did some Google searches and found
this from Sims Wiki.
Seems the issue is in the different regional codes EA uses for different areas of the world. Buying a game from the US will have one code, whereas the UK has another, and the digital downloads one of their own as well. So if you have purchased the game from a brick and mortar retailer and installed from the disc, then went to Origin and downloaded a digital copy, you will have two different regional codes. The link will help you find out which regional code you have and gives links to the correct patches for those areas.
Also, once you have registered your game and expansion/stuff packs with EA, the information will be automatically stored with Origin. If you want you can uninstall any games you have installed from the disc and re-download them from Origin, which would give them all the same regional code and allow you to play without using a disc.