Hi Xhevahir Mehalla,
I suggest you to verify the permission model on key vault and associate to the managed identity that you are using.
Please check :
- Access Policy and Management model thread: https://learn.microsoft.com/en-us/answers/questions/1306020/access-policies-not-available
- Access Policy and RBAC thread: https://learn.microsoft.com/en-us/answers/questions/816270/provide-access-to-key-vault-keys-certificates-and
- Linked service publish https://learn.microsoft.com/en-us/answers/questions/1282897/unable-to-access-azure-secret-key-vault-even-thoug
If the information helped address your question, please Accept the answer.
Luis