This is a very common issue that can occur for a variety of reasons. Let’s take a look at some of the most likely causes and how to fix them.
One possible cause is that your WordPress files are not uploaded correctly. This can happen if you didn’t upload all the files in the correct directory or if some of the files are corrupted. To fix this, try re-uploading all the WordPress files to your server.
Another possibility is that your gallery plugin is not compatible with your current theme. Sometimes, switching to a different theme can fix this issue. Alternatively, you can try disabling all plugins except for your gallery plugin and see if that makes a difference.