If I understand the error correctly, m2ee is expecting you to have the constant Atlas_UI_Resources.Atlas_UI_Resources_Version set in your m2ee.yaml . See for example here how to do it: https://github.com/mendix/m2ee-tools/blob/master/examples/full-documented-m2ee.yaml#L469
Have you renamed, deleted, or moved Atlas_UI_Resources from your App Store modules?
If not, have you moved, deleted, or renamed the Atlas_UI_Resources version constant in Atlas_UI_Resources?
It can't find that constant so is complaining.
A quick fix may be to re-download the module from the Mendix Marketplace.