Since juvenile stage is very short, it's possible that she's an adult already (I've never seen an RB not walk in juvenile stage, but since the stage is so short, I'd say it's possible). Is it just that she doesn't walk often or has she never walked? Each Pleo RB has a unique personality, so some are definitely lazier than others and if she just reached this stage, it may be a little while before she actually decides to walk. Make sure you're running her close to the time you've set as noon, since I notice that my RBs are much more active then. Also if you're cuddling and petting her a lot, give her a bit of time alone. Pleos will often stay where they are if they are being petted and therefore have no reason to move.