Mashed potatoes are like glue.

Karl, you probably overworked the potatoes in the mixer and the starches got released too much. It happens often with the mixer. I am afraid that it is a difficult thing to fix. You could add an egg or two, and some shredded cheese, a pinch of nutmeg, make them into patties or gnocchi and finish in the over.

All hope is not lost! Here are some tips from one of our posts:

Make a well in the top of gluey potatoes, put a pat of butter in it to melt, and sprinkle on a little paprika. This will hide all ills. And, as with the aforementioned turkey, don't forget the gravy.

https://food52.com/blog/4978-5-thanksgiving-disasters-and-how-to-fix-them

I would suggest adding more cream or milk and butter and mixing until they come to the right texture! What recipe did you use?