Some tenants will be unable to provide a positive reference from a previous landlord. If the tenant is a first-time renter or new to the UK, they will be able to pass reference checks without a landlord reference but will be a Caution risk result. This is because having no landlord history to rely on is riskier for the landlord.
If the tenant has rented recently but cannot provide a positive landlord reference, the risk may be high and they may fail reference checks altogether.
Related article: What happens if my tenant fails referencing?