Unfortunately I don’t have any control over the app download and update process. The App Store is operated by Apple and the downloaded or updated apps are stored on Apple servers.
A possible workaround is to restart your Mac and try the download or update again.
If you’re trying to update, a possible workaround is to move the app to the bin and then download it again from the App Store.
If you’re unable to solve the issue, you should try to contact the Apple Support. They might ask you to contact the app developer first (that’s what they usually do when a third-party app is involved); if they do, you can link to this page and emphasize that since the update is managed by the App Store and the App Store is an Apple app, only Apple can help.