Worried about beloved maple tree---diseased?
I am afraid there may be some internal rot happening. This is not something we can diagnose from a photo. You need to have a certified arborist make a house call and a diagnosis. Go to this page and click on Find An Arborist. You can put in your zip code to narrow the search: www.treesaregood.org/
Using this site and your link, don't see a way to find an arborist by zip, just by country which seems inefficient and unhelpful.
Any order advice?
I Just went to the link and you did not go far enough. You click on USA, then state and city or at the city site go to the right and put in your zip code. It will bring up a list. I just did it with my own address/zip code. Try again and follow directions.
You also could check out this link to Wetwood: https://extension.umn.edu/trees-and-shrubs/non-harmful-tree-conditions