Translation:If it is important to the individual, it is also important to us.
"Important to" is a little different from "Important for" and they can't always be used interchangeably. I think it would be better to use "important to" in general and for sentences like this, while "important for" requires a cause. For example, studying is important for me to succeed. What do you think?
There is a reason why something is important for someone, but that reason (clause) is not required. One doesn't have to say why something is important for him/her.
I also don't see why 'this' and 'it' can't be interchangeable here and marked as correct.
wonder why this is marked wrong... If this is important to the individual, it is important also to us
report it. Moving the "also" might sound more natural, but I think your way is acceptable.
The לנו at the end of the recording is cut off for me so it sounds like לה. Makes it annoying for the "type what you hear" type problems.