New flow created in default (app based) environment is unable to incorporate data from legacy (web based) environment.
When a new flow is created, using the contact records, many of the customized fields created on the legacy app are unavailable. As a result, there is no way to implement the conditions needed for a flow.
For example, use contacts, for all records where contact type = client, and next appointment date contains data, then send email. I'm unable to locate the "contact type" or the "next appointment".