Hi,
I had the same problem but for me the issue was related to the ports.
basically in the instance you can see all ports opened for different connection types. I had 3200 for GUI so i assumed instance 00 is the one I should also use for the HANA studion connection.
However, for the HANA connection the port was 30215, so I had to chnage the instance to 02.
Hope this will be helpful.
Regards,
Andrei