Did you put it in the BASS folder or just in the plugins-folder? Maybe you misunderstood the post?
In the “bass” folder is a readme-file stating:
In order to install a BASS.DLL plugin, place the .DLL file in this folder.
So I will edit @Liam 's post to make it more clear where to put that dll in… 
yepp, I feel my self a bit stpd, but I will try that, you was right just droped in Plug-in folder not in BASS
No worries… please report back! 
MP4? I thought this was about…
See #13.
You have liked this…
I’m in favor of addressing the main problem. Otherwise we won’t make any progress here.
To come back to the topic:
Do your folders @Sairamark look like this?
C:\Program Files (x86)\mAirList 7\plugins\bass\bass_aac.dll
C:\Program Files (x86)\mAirList 7\plugins\bassalac.dll
Hi Liam,
C:\Program Files (x86)\mAirList 7\plugins\bass\bass_aac.dll
C:\Program Files (x86)\mAirList 7\plugins\bassalac.dll<
yes look looks like that
Finally SOLVED in Support!
Anything we happen not to be allowed to know?
22 years old method (Uninstall, reinstall) and thanks for @Liam guidance bassalac.dll (x32) solved the problem as on same way as they are posted above!