Having issues while trying to move App MasterUser to ServicePrincipal using .NET Core

AdalServiceException: AADSTS7000215: Invalid client secret is provided

One or more errors occurred. (A configuration issue is preventing authentication - check the error message from the server for details.You can modify the configuration in the application registration portal. See https://aka.ms/msal-net-invalid-client for details. Original exception: AADSTS7000215: Invalid client secret is provided.
Trace ID: 0d451672-16a9-4c5a-a21f-14caccc30d00
Correlation ID: c288dc19-b89e-4c42-a1a0-e2923a257253
Timestamp: 2021-02-12 09:27:45Z)

at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
at System.Threading.Tasks.Task`1.get_Result()
at AppOwnsData.Services.AadService.GetAccessToken() in C:\Users\pksaa\Downloads\PowerBI-Developer-Samples-master (3)\PowerBI-Developer-Samples-master\.NET Core\Embed for your customers\AppOwnsData\Services\AadService.cs:line 65
at AppOwnsData.Services.PbiEmbedService.GetPowerBIClient() in C:\Users\pksaa\Downloads\PowerBI-Developer-Samples-master (3)\PowerBI-Developer-Samples-master\.NET Core\Embed for your customers\AppOwnsData\Services\PbiEmbedService.cs:line 33
at AppOwnsData.Services.PbiEmbedService.GetEmbedParams(Guid workspaceId, Guid reportId, Guid additionalDatasetId) in C:\Users\pksaa\Downloads\PowerBI-Developer-Samples-master (3)\PowerBI-Developer-Samples-master\.NET Core\Embed for your customers\AppOwnsData\Services\PbiEmbedService.cs:line 43
at AppOwnsData.Controllers.EmbedInfoController.GetEmbedInfo() in C:\Users\pksaa\Downloads\PowerBI-Developer-Samples-master (3)\PowerBI-Developer-Samples-master\.NET Core\Embed for your customers\AppOwnsData\Controllers\EmbedInfoController.cs:line 45