If you have uploaded OS and facing this issue, this can be solved. I did it myself.
You dont have to downgrade your OS OR reset your phone.
Go to Settings>emails+accounts
Hope you will see "Attention required" error on your mail account. If YES, perform following steps.
Hope you could have registred your marketplace/live id with any e-mail account initially, you have to remeber password for that account.
you can see your e-mail id from the above option(Settings>emails+accounts).
Go to your LIve ID account & try to login with the credentials. Once you login, click on Verify your email address.
get it varified from your e-mail account which you have used. in my case I used gmail id.
Once this is done change the password of your account in windows live id site.
Settings>emails+accounts>Windows Live>provide new password & try to login.
be sure you are connected to internet, it will update & it will work fine, then you will be able to all those thisngs from marketplace.
If you have used the dummy mail ID(as it was not madatory with previous version of Mango), create the same e-mail account in windows live id.
I have looked at and tried your solution, but it is not working in my case, since windows during the update somehow decided to use a 10 - 15 year old account ........@live.com.
I have tried to get Microsoft to reveal the password for that old account without any success.
Happy to listen and try any solutions to this mess.
For which phone model is this? In addittion to the troubleshooting steps provided by 805ab406. This error code appears when trying to download an app and is caused by incomplete information in your Microsoft account profile. To resolve this, sign in to your Microsoft account (formerly Windows Live ID), tap or click Edit personal info, make sure that your Birth date and Home Country/region are completed, and then press Save.
Note: If you see a message indicating that your password is weak, change it to something stronger. If you are prompted to add additional security information, add it.
Just let us know the outcome.