i used quick Assist for helping people, the black screen is for the security i would say.
one solution is to use cmd or powershell if you have local admin access.
if you install software, you have to use silent mode,
if the computer join the domain and in the 'Lan' network, you might consider deploy 'msra'.
if your environment combine Intune or other tools/solution, make sure the device enrolled .
or if you can enable 'allow remote ' = On. ( the computer connects a trutest Lan network), then you can remote to that pc .