Welcome to the forum!
The eyepiece you purchased is probably one that has been sitting on a shelf somewhere for a long time. I was told when I called customer support related to the same issue that registration is not necessary any more for something like that. Plus, there is no place on line to do that now. Just keep a receipt from whomever you bought the eyepiece from as your proof of purchase.
With a large item, like a major telescope purchase, there is probably a mail-in card. However, I have not bought a large scope in a long time, so I am not sure how that works.
When the Meade 4M Forum was first set up, there was a charge for a certain level. I never did find out what all the benefits were supposed to be. I do know that I recieved a nice little carry bag, a three inch patch for a shirt or jacket, and maybe a pin of some sort. In a year or so, that charge went away as did that high level with its bag and other items.
The Meade 4M Community Forum is free.