My guess is that it could be related to crossdomain or CORS setup (http://www.html5rocks.com/en/tutorials/cors/)...SAP MII does support this and this is outlined in the following notes:
Ranking | Application Area | Number | Short text | Released On |
| MFG-MII | 2158379 | 05/04/2015 | |
| MFG-MII | 2169416 | 07/07/2015 | |
| MFG-MII | 2263727 | 02/02/2016 | |
| MFG-MII | 2206302 | 09/01/2015 | |
| MFG-MII | 2213270 | 10/12/2015 |
You may have additional credential and security management on the HCP side but the authorization error isn't detailed enough to show which layer generated the 401 response.
Sam