[BUG] UnscheduledInvocationReason: IsPastDue and process does not restart

# Transfer

This issue has been transferred from the Azure SDK for .NET, [#22590](https://github.com/Azure/azure-sdk-for-net/issues/22590).

## Please be aware that @sjuarezgx is the author of the original issue and include them on any questions and replies.

TargetFramework : net5.0
AzureFunctions Version : v3
Function App platform: Linux
Consumption plan
Microsoft.Azure.Functions.Worker.Extensions.Timer : 4.1.0
VS 2019

Hi
I have a timer trigger function which is scheduled to run once every 10 minutes, and according to the recommendations, the useMonitor property is set to "true".

"bindings": [{
"schedule": "0 */10 * * * *",
"useMonitor": true
"runOnStartup": false,
"name": "TimerInfo",
"type": "timerTrigger"
}]

I have the following error every time the function is triggered (I can reproduce the problem locally also)

[2021-07-10T15:05:17.825Z] Trigger Details: UnscheduledInvocationReason: IsPastDue, OriginalSchedule: 2021-07-10T11:50:00.0000000-03:00
[2021-07-10T15:06:16.410Z] Starting worker process failed
[2021-07-10T15:06:16.413Z] The operation has timed out.
[2021-07-10T15:06:16.452Z] Failed to start a new language worker for runtime: dotnet-isolated.
[2021-07-10T15:06:16.455Z] System.Private.CoreLib: The operation has timed out.

If I set useMonitor = false, then IsPastDue is false, but the ScheduleStatus of my timer is null so I get null reference exception.

I think that this problem is mostly happening on linux platform.

I think that the expected behavior is that the function should run (having useMonitor TRUE ), and in case there is a "past due" it should retry without the worker process to fail.

Besides, I don't know why ScheduleStatus is null when useMonitor = false.

Thank you very much
Sabrina.