Read the documentation for CancelationTokenSource.CancelAfter:

this method will throw an ArgumentOutOfRangeException when: delay.TotalMilliseconds is less than -1 or greater than Int32.MaxValue (or UInt32.MaxValue - 1 on some versions of .NET). Note that this upper bound is more restrictive than TimeSpan.MaxValue.

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your code in CancelationTokenSourceFactory.CreateTokenSource does this check:

if (timeSpan.HasValue && timeSpan.Value != TimeSpan.MaxValue)

this check for TimeSpan.MaxValue seems totally pointless here, if timeSpan is anything between ~2147483647 and 922337203685476 milliseconds long this will still just throw a ArgumentOutOfRangeException.

I suspect that this check was intended as a way to prevent creating a cancellation timer that never triggers in the CancellationTokenSource, which should look like this:

if (timeSpan.HasValue && timeSpan != Timeout.InfiniteTimeSpan) //Timeout.InfiniteTimeSpan is -1 milliseconds