Can you provide more details or a link to code if open source.
In general you export a klib not an aar, aar is intended to be consumed only in Android target. A klib encapsulates all targets.
However, what you call "export"? You mean you are creating an aar file and copy/paste it in another project.
It is better to use maven or some repo to do that. I am not sure if you can manually copy a klib and just consume it from a client project. Although is possible in theory