The RCT3 damper has Rebound adjust, Compression adjust and a 3 stage lockout.
The compression adjust is low speed adjust which is independent of the lock out.
The lock out has three modes open, mid and lock.
I can’t remember if the lockout has an adjustable threshold or not? I think the low speed adjuster kinda works as the threshold adjuster too ie when low comp damping is used it equates to a lower threshold when locked out.
Make sure the blue dial is all the way round on lockout and not on mid setting. Its not a absolute hard lockout but it should be a very noticeable difference in the fork feel, almost locked out even on the lowest threshold setting.
If there is no significant difference between open and lock then it’s possible that the damper is broken.