You need to use a filter that returns those properties. The default filter does not.

Also, the API is at version 2.2. You should use that unless you've a very good reason not to.

So try, for example:

http://api.stackexchange.com/2.2/users/55075?site=stackoverflow&filter=!G*ky*lRuarbDJTpnwEtY-a05oz

Or:

http://api.stackexchange.com/2.2/users/55075?site=stackoverflow&filter=!-*f(6q0h9HBe

For your URL.

For more information about easily creating custom filters, see this answer.

You need to use a filter that returns those properties. The default filter does not.

Also, the API is at version 2.2. You should use that unless you've a very good reason not to.

So try, for example:

http://api.stackexchange.com/2.2/users/55075?site=stackoverflow&filter=!G*ky*lRuarbDJTpnwEtY-a05oz

Or:

http://api.stackexchange.com/2.2/users/55075?site=stackoverflow&filter=!-*f(6q0h9HBe

For your URL.

For more information about easily creating custom filters, see this answer.