image won't alter in P-shop

I received a pdf that I was asked to modify in p-shop CC version 41.2 . I is a color rgb image that I was successfully able to adjust the curves on… but every additional adjustment I laid on it, it displayed the effect then when I chose “apply”, it reverted back to the first adjustment. Nothing I could do to it would allow any new adjustments to take. Has anyone ever run into this?
mh

if you save it as a tiff or jpg, close photoshop and reopen and retry the adjustments, does it work then?

I did convert it to a tif. saved it and closed P-shop then reopened it. No change. it has never happened before and hasn’t happened since. Bizarre.
mh