MixedRealityPortal.exe faults

Hi,

I cannot get the Mixed Reality Portal to start; every time I run it I see the window app outline for a second, and then it crashes. Here's the relevant event log entry:

Faulting application name: MixedRealityPortal.exe, version: 10.0.16299.125, time stamp: 0x5a29baec
Faulting module name: MixedRealityPortal.exe, version: 10.0.16299.125, time stamp: 0x5a29baec
Exception code: 0xc0000409
Fault offset: 0x0000000000017902
Faulting process id: 0x34bc
Faulting application start time: 0x01d37559f3862375
Faulting application path: C:\WINDOWS\SystemApps\Microsoft.Windows.HolographicFirstRun_cw5n1h2txyewy\MixedRealityPortal.exe
Faulting module path: C:\WINDOWS\SystemApps\Microsoft.Windows.HolographicFirstRun_cw5n1h2txyewy\MixedRealityPortal.exe
Report Id: be90e653-f962-49a2-a3f5-a012ac667912
Faulting package full name: Microsoft.Windows.HolographicFirstRun_10.0.16299.125_neutral_neutral_cw5n1h2txyewy
Faulting package-relative application ID: App

I've tried uninstalling and re-installing the Mixed Reality and running system file checker, but still get the same results.