Magnesium oil doesnt work for me anymore

I started a using ancient minerals magnesium oil a few weeks ago. I got the ash like residue which indicates that it was successfully getting absorbed into my body. Now i no longer get that residue and the oil just sits on my skin. Do you need to take a break from the oil? Maybe i'm deficient in something that works along with the magnesium such as calcium therefore my body is rejecting the magnesium?