Sam, I'm having similar trouble with Specialized battery charging socket covers for 2017-2021 Vado/Como batteries. I believe it is pretty easy to reinsert this small plug into the battery hole. I help myself with a tiny flat screwdriver to force the cover plug back into the hole.
Put a small bit of dielectric grease on the two protruding 'pins' on the rubber cover. This will progressive get easier to insert and remove the more times it is used. On your Multicharger hard plastic cover, which is going to break soon, just get the new upgrade cover with the rare-earth magnets incorporated into the cover assembly. Had to replace my wife's Nevo3 charger port cover early-on.