A required file could not be downloaded while installing SQL Server 2019 Developer

Open PowerShell as administrator and run

Set-ItemProperty -Path 'HKLM:\SOFTWARE\Wow6432Node\Microsoft\.NetFramework\v4.0.30319' -Name 'SchUseStrongCrypto' -Value '1' -Type Dword

Set-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\.NetFramework\v4.0.30319' -Name 'SchUseStrongCrypto' -Value '1' -Type Dword

Source https://techcommunity.microsoft.com/t5/sql-server/sql-server-installer-unable-to-download-the-required-files/m-p/2120065/highlight/true#M890