When you try to access Veeam ONE Web UI, the following error occurs:
Cannot open database requested by login. The login failed.
Veeam ONE Web UI configuration is missing information on the account used for SQL authentication.
To modify configuration settings, follow the next steps:
Launch the Veeam ONE Settings utility available in the following location:
C:\Program Files\Common Files\Veeam\Veeam ONE Settings\VeeamOneSettings.exe
Open the Web Identity tab, re-enter credentials and click Save.