Time shows as 00:00:00 across whole x axis

I have created a scatter plot with time on the x axis. I have formatted the corresponding cells as time 00:00:00. I have gone into format x axis and changed the number category to time 00:00:00.

The x axis shows time as 00:00:00 across its entirety.

I would like time to go up in increments of 6 hours.

File attached.