On the block configure page at /admin/structure/block/manage/menu/menu-about/configure, which you get to from Home » Administration » Structure » Blocks, the documentation below the textbox i "Show block on specific pages" is wrong or misleading, at least when applied to /user urls. The documentation implies that if you want to display the block on blog pages, then "blog" is an OK entry. But if you want to display on a blog personal page, then you should use blog/* as the entry.

For /user, which you typically get to by clicking My Account after logging in, if you did not specify user/* then the block will not display. The example implies that it should work but if you use just "user" in the field, then the block will not be displayed. I'm not sure if this is just an exception related to /user behavior or if it's universal for all URLs like this. If it's specific to the /user page, then I would add the following to the help text: "For user pages, you must use user/* even if no node id is specified."

To reproduce, put "user" (without the quotes) in the field and check "Only the listed pages". Then try logging in and going to your My Accounts page or just add /user as the path on your address bar.

Thanks,
Norm