We're sorry to hear that you don't see Tenure reported in Sherlock. Tenure is one of the most important data points when assessing product engagement!
The reason you are not seeing Tenure in your account is because you are not sending Sherlock a createdAt trait from Segment - either at the user or account level.
You can learn more about how we calculate Tenure here, but the first step is recording the createdAt trait for your users and accounts.