First, try typing "reload" into Alfred, which will refresh the application cache.
If that doesn't resolve the issue, there's probably a bit of confusion in your Mac's metadata index, so pop to Alfred's Advanced preferences, and click the "Rebuild macOS Metadata" to rebuild your Mac's index. This can take up to an hour, then type "reload" again, and let me know how you get on.
@matias Alfred relies on your Mac's index, so if it's a little out of date, or corrupted, apps can be missing from results.
The first way to reindex just a single app is to pop up Spotlight preferences to the Privacy tab, drag the app (or the Applications folder) in, wait 30 seconds, then drag it back out. Wait a few minutes, and your Mac should reindex that folder. Once that's done, type "reload" into Alfred, as Alfred keeps an application cache for quick results.
If this doesn't resolve the issue, take a look at step 4 here, which is a full reindex:
https://www.alfredapp.com/help/troubleshooting/indexing/
