Interest groups from Mailchimp form not synched

Hi,
I created a form within the plugin.
Form works for merge fields and opt-in but checkboxes and interest groups are not synched.
Form looks like this:
“<p>
<label>M?gliche Wochentage</label>
<label>
<input name=”INTERESTS[e466c55cc4][]” value=”c8a608d9e2″ type=”checkbox”> <span>Mo</span>
</label>
<label>
<input name=”INTERESTS[e466c55cc4][]” value=”f9913f78ed” type=”checkbox”> <span>Di</span>
</label>”

I also bought the “User sync” add on, but that seems not to sync that kind of fields from the user profile, right?

Thanks for any hint

Klaus