It would help to know what course and which exercise set (or quiz or test) this happened in.  Or was this a practice problem in an article? You could even include a screenshot.

KA Reimagined is still supposed to have hints.  When the student's answer was marked incorrect, did the student try pressing the Hints button? Was the Hints button not there when the student was answering the question? (or if this was a practice problem in an article, was there an Explain link?)

~ Janice, KA user who's responded to hundreds of Questions in 6th grade math over the past 18 months 

Unfortunately, the new interface is buggy as when I went to screenshot the issue, it now only shows 2 questions out of what used to be 4 or 5 questions. It also now marks the “-2x - 3” as correct where it was incorrect before.

This is Algebra 1, Unit 8, Inverse Functions.

Wow, that inconsistency in the interface seems incredibly unhelpful and frustrating.

I suggest posting a support request to KA staff using the "Report a problem" in the upper right of this screen.  (If you want to, you can wait to see if any users have useful suggestions or if KA staff eventually respond here; when I've looked back at similar posts in this forum, my memory is that some got a response from KA staff in a day or a week, while others are over a year old and still have no response from KA staff.)