Since this is a relatively old version of photo shop, the file may not have a high prevalence in the avast database, it may also not be digitally signed. The more of the things the autosandbox is looking at the more likely it will recommend running a sandbox check.
Given the VT results and the fact that the autosandbox process is controlled in the first instance by the file system shield (FSS), the suspect.exe file is scanned before it is allowed to run. If it were infected, it could/should be detected by the FSS, so one reasonable thing in its favour is it hasn't had a definitive detection.
You can use the dropdown selection to have avast open it normally.