Hi Mike,
As per your details in very first post, these seems to be two different issues:
1. iSQL Access issue with SYSTEM User
Please try resetting SYSTEM user account to fix this
HANA Tutorials: How to reset the HANA SYSTEM User password.
2. Hana DB Studio Connectivity (System Can not be reached).
Please check if you are providing correct details in studio for your hana db (servername, port). If you have any other user which can be used (apart from SYSTEM) for creating connection entry in studio.
Thanks,
MPS