Umm, are you saying only the speed bearing fits in your Legacy II?
They should all fit.
Or no bearing fits? Make sure there is no bearing in the yoyo. Take a cotton swab and dip it in Rubbing Alchohol. Then run the seat until it looks clean.
Or just see if there is something in the seat or if something looks deformed. Like a small bump or a little spike, or a chip.
If it’s new, contact where you bought it from and ask for an exchange.
If it’s not new, you need to figure out what the issue is.
Is the yoyo and/or bearing not spinning? Maybe the solid spin axle has come loose. Maybe the sides of the bearing seat need a bit of shaving off of some plastic? But that would indicate a manufacturing defect.
Also check that area for stuff in there that shouldn’t be in there.
The Legacy II should work fine with any C size bearing.