I have two apps, one i started last year and on i started this year. The new one builds on the app centre againsst net standard 2.1 and the old one 2.0. I tried setting the target of the old one to 2.1 and it complained that the sdk it was building with didn't support that. I tried setting a global.json and same problem. It is almost as if the old build/project is configured to use an old SDK somewhere and the new project a newer SDK. What doi change and how do I change it?