A few things to try:

I suggest you enclose the path to the INI file in quotes, just in case:

/ConfigurationFile="C:\tempdir\config.ini"

I add params for QuietSimple and licence agreement (these can also be set within the INI file)

/QS /IACCEPTSQLSERVERLICENSETERMS

Ensure the UI mode is commented-out:

; UIMODE="Normal"

Can also experiment with enabling/disabling

QUIET="True"

in the INI file.

Also, try starting Powershell with local administrator rights.