Hello kietngo,
We hope you are doing great.
The error message you’re encountering, “Invalid backend response. Data is not JSON,” suggests that there might be an issue with the file or the upload process.
To assist you further, please enable the debug logs and attempt to reupload the file again. This will log the error. Additionally, please let us know where (location/path) you’re trying to upload the file from.
Furthermore, if possible, could you please share the header.php file with us?
Once we receive the debug logs and the header.php file at [email protected], we will be able to better understand the issue and provide a more accurate solution.
Regards,
WP File Manager Support Team
