Adding Google Play Support after campaign started.
Hello, I've had a campaign running for awhile and noticed there is no way to add Google Play support after the campaign is running (the checkbox does not work). I think this severely affecting my conversions and it's something I didn't notice until after starting. I'm not talking about getting conversion stats but, in general. I'm using promotional credit and I'm not sure if I'll lose it if I stopped the campaign.
You are correct that the promotional credit can only be used for one campaign. Play support can't be added once the campaign starts running. Please note that, unless you have the mobile ads SDK integrated, conversions from Play when Play is enabled would not be tracked in Advertise Your App. Thus, adding Play would potentially affect your impressions and clicks but not conversions, as reported through Advertise Your App. (You may be receiving conversions from Play, but Appstore and Advertise Your App would not be able to report those conversions to you.)