dc="Домен"тут кавычки не нужны, пробелов между частями DN быть не должно.
This worked for me on Android.
1. Go to Settings > Exchange
2. Uncheck 'Use Skype for Business credentials'
3. Enter your email address and password manually
4. Press OK
Backup-SqlDatabase -ServerInstance "Computer\Instance" -Database "MainDB" -BackupFile "\\mainserver\databasebackup\MainDB.bak" -Credential (Get-Credential "sa")