Dear John,
First, assign the Power User authorization thru PFCG
Object :GRFN_USER -
Activity : 02 - Change: This is used for Power User authorization
If with this autorization you are able create a risk proposal, likely your problem is autorization.
Also, you can check if you activated the SPRO's configuration thru the link :
Governance, Risk and compliance
Risk Management
master data setup
Activate Risk Proposal and/or Ad-hoc Escalation
I hope those informations I sent was helpful .
Regards,
Karina Atonaidan