In all this time I hope you’ve been able to solve it, answering for anyone to come, but let me know, I could lift one and send pics!
I have two of them, I’ve done it once with one after liquid spill (not mine, JIC) to give it a good clean and if IRRC there’s one way the plastic tabs fall flat and other where they stick up. In that position the space bar should click right in. I don’t remember if I fitted the tabs on the keyboard or in the key first, only one of those worked. Try dissembling another key to check, as I remember small keys being similar but easier.
Cheers!