Hi there,
You may want to include the URL so people here can take a look at your ad and give some feedback, maybe

Ok thanks for that I will edit but here it is as well-https://nzdaisuki.com/classified/house/ad/live-exchange-86/1-bedroom-full-kitchen-lounge-and-bathroom-77162

Did you use the same words/ad but weren't contacted by many people? If so, I honestly have no idea what's wrong. My personal opinion is I'd like to know these things if I were to apply.

- A little more specific information about the jobs and the paid extra work would be appreciated. E.g. cleaning (X rooms of vacuum, bathroom, kitchen, etc.), laundry, grocery shopping...
- Working hours (evening? morning? anytime?)
- What's there in the downstairs

Also, you could mention that your previous exchange person was Japanese (if so) and how long he/she stayed there. People may have thought the ad was a little suspicious. If they knew this was a replacement position, they would be much encouraged.

Another suggestion is to post in the section of [オーペア/ボランティア/エクスチェンジ] (au pair/volunteer/exchange) as well. Please refer to the attachment.

Hope this helps!