You might have trouble accessing a campaign in Google Ads Editor if the Conversion Optimizer was enabled after you last downloaded the campaign.
To fix this issue, please download your full Google Ads account again into Google Ads Editor.
You can use Google Ads Editor to update the ads and keywords in a Conversion Optimizer campaign, or to change your maximum CPA (cost-per-acquisition) bids. However, it isn't possible to enable or disable the Conversion Optimizer in Google Ads Editor, or to create a new Conversion Optimizer campaign in Google Ads Editor.