If you migrated Veeam databases from one server to another or simply receiving the following error "Task failed Error: Cannot complete login due to an incorrect user name or password."
1. Open Veeam Backup & Replication software
2. Click on Backup Infrastructure on the left hand side
3. Expand Managed Servers
4. Expand VMware vSphere
5. Click on Standalone Hosts
6. Choose the server with the issues, right click and choose properties
7. Click Next
8. Confirm username and re-type the password, this is your issue.
9. Click Next, then Finish
10. Run Backup Job again.