ReadyNas NV+ RND4000 v3: admin login does not work

After not having used my RND4000 for a few years, I'm trying to relink it in my little network (via Apple Time Capsule), managed from an iMac.

I downloaded the newest version of RAIDar (6.5.0) and after a factory reboot fied up the tool, which gives me an encouring view:

However, since my iMac can only link to it as 'guest' I wanted to enter the Admin Page... and that's where it goes south: I obviously don't remember the userID nor the password, however, with al the info online, I tries OS reboots, factory reboots, ... nothing helps, it seems stuk on the old userID/password, and won't revert to 'admin/password'... I always go back to the log in pop up:

So I'm stuck with a NAS drive that I can see but not use...  Several factory reboots later, still no change...

I found somewhere that the firmwre can/should be upgraded to RAIDiator-4.1.16 -- downloaded the thing, but arently cannot install it without getting into the RAIDar tool as administrator :-(

Any ideas/suggestions?  If I'm doing something wrong/stupid, please let me see the light (preferably in plain english, I'm not an IT guru :-)  I can handle step by step deals, though ;-) )

Thank you in advance for any input/feedabck you'd like to throw at me!

 

Kind regards, Ivo