Disease or pest damage on Gingko is unlikely. Root issues on a newly planted tree, however, are common. “Failure to establish” is a phrase I hear used, sometimes even years after a tree has been in the ground. Troubleshooting the problem with your tree now is a good plan. At a glance, this looks like an issue with water-uptake, likely roots or trunk damage. To figure this out will require some discussion about the tree at purchase (bare root or root-bound pot or ?), how you prepared the site, and how deeply you planted it. This publication from Pacific Northwest ISA about how to plant a tree is the basis for most questions you’ll be asked: https://pnwisa.org/tree-care/adding-trees/planting/ This discussion and possible multiple photos back-and-forth will be easier with email and/or phone calls. I suggest you contact your County Extension Service Master Gardener Volunteers. You can give them the link to this page to avoid having to start over. https://extension.oregonstate.edu/mg/metro/have-gardening-question