The average conversion rate industry-wide is typically between .75% - 1.25% so if an ad is underperforming, there's typically a reason for that. It could be any or a combination of the below reasons.
The audience the brand is targeting is not aligned with your listeners
If that's the case, you can try to broaden the talking points to apply to a more general audience and/or connect with your listeners by using words that appeal to them.
The ad is difficult to understand or there is an issue with the audio
This can be for a variety of reasons such as:
an issue with the mic or volume
background noise such as music or more than one person talking at once
it sounds sped up and it's difficult to understand the message
It is a host-read-ad that follows a non-host-read ad
Non-host-read ads usually perform lower than host-read ads in podcast advertising and listeners are more likely to skip ahead once they hear a non-host-read ad, especially if it's a pre-roll ad without any intro to the episode. For better conversions, place your host-read ads before the non-host-read ads.
The ad lacks enthusiasm, ethos, and/or energy (One of the most important factor)
Although brands provide talking points, it is usually best for conversions when listeners feel like you're having an organic conversation about the product or brand you're promoting in your ads. Hosts know their audience best so use that voice, and continue the conversation by taking about what you're promoting with a genuine voice.
All ads are different. Some topics, like mental health or disease prevention, require a more earnest tone whereas others, like a language app, may take on a more light-hearted voice. You can connect with your listeners by sharing an anecdote in your ad about a funny thing you said when you were traveling abroad and didn't speak the language. When talking about something serious such as mental health and wellbeing, you can share a statistic so your listeners who may appeal to the ad feel like they're not alone, while also speaking to the importance of self-care.
Not all ads will allow you to test the product but you can still speak to the general benefits and sound passionate about the ad you're serving. You can talk about brand values, ethics, or the importance of the benefits. For example, if you're promoting a resort located on the other side of the country that you haven't visited, you can still talk about how taking that impromptu trip with your best friends (or co-host) was the best decision you made and so on that note, you're excited to share that your listeners have a discount code for a getaway and exclusive access to the resort's infrared sauna.
You had a rough week and recorded the ad last-minute because (you're human) and that's how life is so you just rushed through it to make sure it was published on time but you didn't really put much effort into it. That's ok, just re-record it once you're feeling re-energized!