I bought one of these a couple years ago (new old stock from a local dollar store) and I still have the manual!
I haven't used the card, but here's what the manual says:
'Instruction for Use'
To access V-Mem, you will need to hold down any button on the controller connected to Controller Port #1, and then turn the Playstation ON. Continue holding the button until the V-Mem title screen appears. To bypass V-Mem, simply power up the Playstation without pressing any buttons on the game controller.
I don't have my Playstation hooked up at the moment, but I can try mine out later if you're still having problems.