Most upload failures come down to one of three things: the file exceeds your PHP upload limit, the destination folder has the wrong permissions, or your FTP/SFTP connection is misconfigured. Start with File Manager since it rules out connection issues entirely, then work through the checks below.
Check the file size limit first
If the upload fails immediately with an error about file size, or hangs and then times out, you're likely hitting upload_max_filesize or post_max_size. These are PHP settings, not portal settings, so they apply to uploads done through WordPress, a custom app, or any PHP-based upload form. They do not apply to raw FTP or File Manager transfers, which aren't bound by PHP limits.
To raise them, log into cPanel and go to Software → MultiPHP INI Editor. Select your domain, switch to Editor Mode, and adjust upload_max_filesize and post_max_size. Set post_max_size equal to or larger than upload_max_filesize, since a form with several fields plus a file needs the total POST size to cover everything.
The portal's PHP Version tile only switches the PHP version itself (7.4 through 8.3) per domain. It doesn't touch these limits, so if you're only in the portal, you'll want cPanel for this step.
Check folder and file permissions
If the file size isn't the issue, permissions usually are. Standard permissions for a web-accessible folder are 755 for directories and 644 for files. If a folder was set to something more restrictive, or if it's owned by a different user than the one attempting the write (common after restoring a backup or moving files with FTP), the upload will be rejected even though everything looks fine from your end.
File Manager lets you view and change folder and file permissions on most hosting accounts. Avoid setting anything to 777 even temporarily. World-writable folders are a common entry point for malicious file uploads and a security risk.
If you're uploading into a WordPress wp-content/uploads subfolder, confirm the parent folder didn't lose its permissions during a plugin update or manual edit. WordPress creates year/month subfolders automatically and expects them to inherit sane permissions from the parent.
Check your FTP or SFTP connection
If you're uploading over FTP and the connection itself is failing (not just individual files), verify you're using the correct FTP credentials and that you're connecting to the correct host and port. Passive mode FTP clients sometimes stall on large files or flaky networks; if uploads consistently die partway through, try SFTP instead, or switch your client's transfer mode.
A partial upload can also look like a permissions error. If a large file uploads to 80% and then stops, check your client's timeout settings before assuming it's a server-side block. Re-uploading the same file at a different time of day or over a wired connection instead of Wi-Fi is a quick way to rule out network flakiness.
Check disk space
An upload can fail or show a vague error if the account is out of disk space. Check your available disk space on your service detail page in the portal. If you're near the limit, clear old backups or unused files before trying again.
When to contact support
If you've confirmed the file is within your PHP limits, the folder permissions are correct, your FTP connection is stable, and you still have disk space, but the upload still fails, open a ticket from Support in the portal. Include the exact error message, the upload method (File Manager, FTP, WordPress, or a custom script), and the file size. A real person will look at the server-side logs, which can catch things not visible from your end.