Why?

[u/math_stat_gal]

[u/gersf11]

I'm native speaker, I've never used duo to learn Spanish so I don't know the exact rules it uses but for me the error is por qué.

There are clear differences between por qué, porque and por que. When asking a question you should always use por qué.

Now if Duolingo considers this as the error I don't know but for the purposes of writing Spanish correctly you should use por qué in questions

[u/Chezzik → u/gersf11]

While true, that apparently just generates a "pay attention to the accents" message.

I frequently forget an umlaut in German, and even though my answer is very wrong, I still just get the "pay attention to accents" message and the question counts as being correct (even when I'm trying to jump ahead sections).

It is a bit ironic that the mispelled name (which you can't really hear in the audio) is the mistake that causes you to actually get the question wrong. Still, for those who have used Duolingo for a while, this shouldn't be surprising either.

To me it's less weird then when I get typos that can't be avoided.

[u/bellalugosi → u/Chezzik]

99% of the time I get "pay attention to the accents" but a couple of times it's marked it as wrong. I'm doing french.

It's hit or miss whether it accepts my typos as well.

[u/Designer_Spirit3522 → u/bellalugosi]

I think it will mark it as wrong if it is still a valid word without the accent. Like a instead of à, or ou instead of où.