Question:

After a Vault-to-Vault connection is established, a user tries to migrate a Multichannel Presentation from one to the other. The user receives the following error message: - "source_vault_link__v" is not active at target vault.

Answer:

Only users with the System Administrator or Vault Owner user profile are able to activate this field. Please reach out to an Admin in order to either elevate the user profile to one of those Security profiles. 

To activate a document field, use the following document:  Document Field Activation

Related Documentation:

Vault Help Documentation: Working with Shared Fields