After 2 hours, I finally found WHERE to modify the Sandbox settings. The help (search) for sandbox tells yuo a lot of what you can do but NOT how to GET to thos settings in the first place. Sorry to have bothered y’all. I erased my original request here since I was able to finally “releas” a file that WAS not infected but Avast insisted on opening in the Sandbox!
Sorry to get here that late… We are all around the world but we need to sleep some hours a day 
Glad you’ve solved it.