We are getting the below error while trying to deploy SPFX webpart in SharePoint. We are using SharePoint 2019 On-premise.
When generating the package it does not generate any errors but when I upload it to the App Catalog library it gives me the following errors:
There were errors when validating the App manifest.: Xml Validation Exception: 'The 'IsClientSideSolution' attribute is not declared.' on line '1', position '251'., Xml Validation Exception: 'The element 'Properties' in namespace 'http://schemas.microsoft.com/sharepoint/2012/app/manifest' has incomplete content. List of possible elements expected: 'StartPage' in namespace 'http://schemas.microsoft.com/sharepoint/2012/app/manifest'.' on line '1', position '342'., Xml Validation Exception: 'The element 'App' in namespace 'http://schemas.microsoft.com/sharepoint/2012/app/manifest' has incomplete content. List of possible elements expected: 'AppPrincipal' in namespace 'http://schemas.microsoft.com/sharepoint/2012/app/manifest'.' on line '1', position '355'.
