There really isn't that much you can do to interest someone who isn't interested. Depending on your situation you can confront the uninterested stakeholder and bring up, carefully, your perception of the lack of interest. Stick to facts, i.e., "I've noticed you aren't at our meetings. Is there something wrong?"
In any case, continue to communicate with the person; send reports, include in emails, etc. You might also consider discussing this with the project sponsor.