It's a license issue. The OCRPro licenses are yearly licenses and each license has a limitation on the number of pages allowed to be OCR'ed. The SDK will throw this error when the limitation is reached.
Please have the website administrator (or the web service provider) contact us at support[at]dynamsoft.com to renew the OCR licenses.
If you are the developer of the site, you can contact us directly.
OCRPRo Price Info.