When using the Provisioning Server Services Configuration Wizard to join an existing farm, the farm is not listed in the available farm names to join.
This might occur because of the following two reasons:
Issue 1 The account used to run the Provisioning Server Services Configuration Wizard has a database server login but does not have permission to the Provisioning Server database the user wants to join.
Issue 2 The account used to run the Provisioning Server Services Configuration Wizard is not a member of a group specified in the security tab in the farm properties.
- In SQL management studio, under server security, access the relevant login properties.
- Click User Mapping
- Select the Provisioning Server database you need access to.
- Under Database role membership, select at least the db_datareader database role.
In the Provisioning Server console, access the farm Properties and add the relevant group under both Groups and Security tabs.
Read the entire article here on the Citrix knowledgebase.