I assume: you made it harder for you, than it should have been. You wrote:
Ok, I reflashed the remote, and now the little green light does flash.
I see the little green LED going on and off, but nothing happens
The green LED flashing indicated that your OSSC recognized an incomming (compatible) IR command. “Nothing happening” just meant: the incomming command was no default command for any function of your OSSC. But by pressing BTN1 while powering your OSSC on, you can link any recognized IR command with any function of your OSSC.
So there was no real need for your old ViewSonic remote – just 60 seconds of your time to configure your OSSC properly 😉 .