Hi there, @Gebeker, thanks for taking the time to post here.
Can you please check if the photos you added to your Dropbox folder actually synced to the account?
You can check this, by taking a look into your account online. If the files appear online, then the issue lies with the mobile app.
If you don't see them online either, then they probably haven't synced through the desktop app yet.
Let me know what you find and we'll go from there.