Ask HN: Why would my Apple Id password no longer work?

My Apple Id password no longer seems to work. I tried to install an app on my iPhone, I'm asked for my app store password, which is rejected, twice.

I'm at a loss what's going on. I also notice that iCloud and AppleId sites are very slow to load, and many times do not load properly at all.

Does anyone have any idea what's going on? It is that the password is checked online or something, and that check is failing for some network reasons? Is there a way to see it on my Macbook?

Just seems like it is too hard to understand why some Apple stuff can be so unreliable.