According to the developer news on Twitter, Apple seems to have inadvertently caused iOS 14 betas to be pushed to a small number of developers.
The developer stated that Apple directly cleared the content contained in the description file after finding the problem, so the new preview version can no longer be detected after the description file is installed.
— Majin Bu 🤌 (@MajinBuOfficial) June 14, 2020
In addition, Apple has not yet opened the firmware verification of the iOS 14 version, so even if the description file is not cleared, it is estimated that you cannot upgrade the new version temporarily.
Of course, Apple will hold the WWDC 2020 Developer Conference on the 22nd, and the first developer version for developers will be published directly.