Azure Functions Tools gives runtime error using Application Insights 2.16

Got a very simple function to illustrate the problem:
```
[FunctionName("Function1")]
public void Run([TimerTrigger("0 */5 * * * *", RunOnStartup =true)]TimerInfo myTimer, ILogger log)
{
var requestActivity = new System.Diagnostics.Activity($"Test");
requestActivity.SetIdFormat(System.Diagnostics.ActivityIdFormat.W3C);
requestActivity.SetParentId(Guid.Empty.ToString());

using (var activity = telemetryClient.StartOperation(requestActivity))
{
}
}
```
Running that function gives this error:
**Executed 'Function1' (Failed, Id=5d9ccc3f-2e1d-4f0a-b235-6384b86ae777, Duration=4258ms)
System.Private.CoreLib: Exception while executing function: Function1. TestApp1: Method not found: 'Microsoft.ApplicationInsights.Extensibility.IOperationHolder`1 Microsoft.ApplicationInsights.TelemetryClientExtensions.StartOperation(Microsoft.ApplicationInsights.TelemetryClient, System.Diagnostics.Activity)'.**

Downgrading Application Insights to 2.15 or 2.14 solves the problem. TelemetryClient is injected.

This happens on the latest updates of VS2019 (16.8.4). What am I doing wrong here? Or is Functions Tools not compatible with AI 2.16?