Timothy, when you ordered the adapter from Mad Vapes was it the same as the link I sent you earlier?
Mine came with a normal center pin installed on the 510 connection and a separate, slotted center pin which wasn't installed. This second pin had to be inserted on the 808 connection and screwed into the other pin. It would be very easy to not see that tiny pin and have it fall out of the baggie when you remove the adapter.
You could also try to see if your other adapter from V4L was made the same way, assuming you kept it. If so, you could probably use that center pin to fix your new one.