This type of problems are usually caused by other third-party extensions which modify OpenCart modules.
Omtex. We cannot offer a compatibility patch for this extension as it replaces core OpenCart files. The only way to fix this is to bring back the original OpenCart files, which should be handled by the developers of this extension. Please, make sure to completely uninstall omtex before installing OMF. This means that all omtex files in the
/vqmod/xml directory must be deleted before installing OMF. Both extensions cannot work side-by-side on one OpenCart installation.
- Disable OMF temporarily
- Contact the developers of omtex and ask them to completely remove their extension (delete the XML files) from your website.