RelatedTitle this should work...
You can check the site in private browsing to check if the caching issue is in your browser. If it works in private browsing, then it's your browser cache that didn't clear properly.
If it's also broken in private browsing, then it's Flarum cache. A last solution is to manually delete the files via FTP/SSH. You need to remove all assets/*.js, assets/*.css and assets/rev-manifest.json files in your flarum on your server.