I am not sure what is going on here, the aac stream for FIP works for me. The URL you posted is the same (apart from being http rather than https) as that used by Roon.
You say you are using a NAS - I wonder if you are having the ffmpeg issue that can arise with Synology or QNAP, concerning aac streams. Can you play CJSW which is an aac station to check please?
If you do have the problem, there are a number of threads about this, see