I wrote "sade" instead of "sa" and got an incorrect answer. "Sa" is mainly used in spoken language, and is a more informal form of "sade". Both should be correct.
When translating this sentence from English to Swedish, both sade and sa are already accepted answers. But this is the sentence forum for translating from Swedish into English, so I don't understand how you could have had that problem in the first place?
I've passed this problem on to Duo staff, but it seems this may not be all that easy to fix. Stay tuned but don't hold your breath! :)
Where is the sequence of tenses? 'She said that I had good vison' was marked wrong??
The translated sentence starts with "She said...". That it is Reported Speech so the second part of the sentence should be in simple past also. 'She said that I had good vision'.
We allow for mixing tenses when the statement conveys something that's not just true at the specific time noted. This is quite common - for instance, if the appointment was just this morning, it would make sense to presume that your eyesight hasn't changed since then.