Try to clear your EA app cache.
If that don't works only support can help in such a case.
Restarting the router, changing the region to English (if not already set this way), changing Browsers, disabling add-ons especially anti-script and ad-block software could help with the contact attempt.
The link to EA's Support is here.
1. In "Search game or Topic" Search for "EA app".
2. Click on "See all Help Topics"
3. Click "I need help logging in to my EA Account"
4. Choose a contact option, preferable "Chat with us"
(EA help Guide.)
You also could try EAs Support on Twitter or on Facebook.
I've contacted the support on saturday. They gave me some fixes to try, but all failed. Then they told me that they would send my issue to a team to work on it and that I would receive an answer within the day. Well, it's wednesday and I have not receive any reply and the issue is still ongoing.
The error happens because you tried to get the DLC in-game, this is no longer possible, DLC are only handled in the EA app/Steam.
We are talking ME3 of course, do you own the game in EA app or in Steam?
What does it say in the respective app about the DLCs?
(Steam > Right click on MELE > Properties > DLC)
(EA app > Game Library > click the dot menu on the MELE cover > Manage Add-ons)
I have it on the EA app. I already have the only add-on installed, which is the "Extended Cut".
