I also have the same issue in my iPad Pro 12.9 2018 wifi+cellular. This iPadOS 14 has crucial trouble. I have upgraded to iPadOS 14.0.1, but it still remains. I can't get any signal even cellular data. I also have tried some providers yet still have same issue. I really need this feature as my daily job. I regret to upgrade my iPadOS. Please fix this as soon as possible, Apple! 🙏🏻