Difficult one, a lot depends upon the place on the dash and the type of plastic.
I know that if on wood furniture the veneer lifts you can use a warm iron and thick brown paper and iron over the bubble. This works on the basis that veneer is glued to the lower wood and in effect you reheat/activate the glue back into hold the parts together.
Don’t know if it will work or not on plastic depends how the dash is made up.
Another idea would be to inject some glue into the bubble and put pressure on lifted area till set.
I guess you need to think what it will look like when done and how good or bad the repair will look.
Take care!
Maurice, March 2010