Be sure to backup the Mac before doing so.
Installing available system software updates on the Mac can often resolve this if so.
Usually you simply have to log back into the Mac App Store and re-download the app in that situation. For example if you are downloading Google Chrome or Signal, make sure you download those apps directly from the developer website only, do not download them from third party sites. Note if you are seeing a similar but different error message with Mac App Store apps, use this troubleshooting guide instead. Re-downloading the app, rebooting the Mac, installing system software updates, and using the command line are covered here.
