Ditto with the WD40...it should dissolve the adhesive if you let it sit for a few seconds, then you can start to peel from one side...applying more WD40 as needed (don't overdo it). Then to clean any residual WD40 use your regular interior vinyl cleaner that won't leave your dash shiny...you want a mat finish on the dash to prevent glare.
Spray a little on a cloth rag (not paper towel...it will absorb the WD40) and test what it does to your dash in an inconspicuous location...it may help determine how and how much you should use...plus what you may need to use to remove any residual WD40 from the dash after the pad has been removed from your dash.