Sony Addresses their "Welcome Back" Congestion Issues
For some people (like me) there have been errors on the PSN Store when trying to navigate it. This is the Statement Sony has on their site.
UPDATE: Due to high traffic on PlayStation Store, you may encounter error messages or issues. We advise you to check back a little later and try again.
Note: In order to download two games at no cost, you must redeem them from the “Welcome Back” category. The individual titles are still available for purchase outside of the “Welcome Back Program”
If at any point you can’t find the ‘Welcome Back Free Game 1 or 2’ products, the list of available titles or a game you’ve selected, go to your XMB>PlayStation Network>Account Management>Transaction Management>Services List>SCEA Promotions to complete the process.