Set Up Ad Customizers
Google's new Expanded Text Ads that have rolled out don't allow setting device preference, meaning advertisers can no longer write ads specific to devices. One way to fix this it to create a separate campaign that is mobile only (set one to -100% mobile bid adjustment, the other to -100% desktop). This gives you a lot of visibility and flexibility with your mobile ads, but doubling your account size might not be viable for larger accounts. A second solution is to use ad cutomizers, that will dynamically change ad copy based on the device the user is searching from.