Is it very cold where you are and is it a stealth version?
The reason I ask is that all brand x droppers, but particularly the stealth ones are prone to have the lever at the post end freeze/seize up.
Our group night ride on Wednesday involved three frozen up brand x droppers!
The stealth one seems to attract any moisture in the frame onto its lever at the base of the post. It then freezes and you can activate the lever as normal, but it won’t spring back, so the post just becomes a suspension post.
If it is on the brink of freezing/seizing sitting down on the seat can just knock the lever enough to fix it again – hence you can get the post to stay down, but not stay up.
The Brand X posts are brilliant, but they do need keeping clean, well lubed and adjusted to be totally dependable in the winter.