Timer trigger Function App Resulting in Error Code 415 Unsupported Media Type

Question

I have a timer trigger function C# which uses a KQL to call azure resources and add the data in SQL. It was working fine untile lately it started giving unsupported media type error. Does any one know what changes to be done in the code.
I have googled it says content type header is missing but if that was case why it was working fine earlier?

Also I am using the below class for invoking http client request within the timer trigger.
namespace Microsoft.Rest
{
public abstract class ServiceClientCredentials
{
protected ServiceClientCredentials();

    public virtual void InitializeServiceClient<T>(ServiceClient<T> client) where T : ServiceClient<T>;
    public virtual Task ProcessHttpRequestAsync(HttpRequestMessage request, CancellationToken cancellationToken);
}