The steps I posted above are the steps I took.
But not exact..
I imagine if ISQL was able to find it, you may be fighting a permissions issues..
Try running the ISQL command as the Hana admin <instance id>adm.
If you did the process as root and did not chown hdbadm:sapsys /path/to/files/you/createdasroot
hdbadm will not find the .odbc.ini.. Wait the .odbc.ini may be user specific so you may need to put the .odbc.ini under the hdbadm user home direcory?
IF not, I would have to see the .odbc.ini file and the path to the file.
I would also check to make sure HANA can find the property_postgresql.ini
It has been a pretty long time since I have looked at this..
Let me know if you have success or not. I will dig a little into the system.
Good luck!