Error: your license does not include office to pdf permission

We are using pdftron to open files. Previously it was working proper and now for xls files it is giving me error. error: your license does not include office to pdf permission.

XLS files are the only files not working?
What about XLSX files?
What about other files types?
Please provide the entire exception message (which should include the SDK version and platform you are on).

Thank you for your reply.
Yes Both XLS and XLSX are not opening. Previously it was opening without any error.
Other files are opening without error.
Now we are getting below exception message.
error - Exception: Message: Your license does not include Office to PDF permission. Conditional expression: Version : 9.5.0-d580e32f90 Platform : Linux Architecture : AMD64 Filename : Function : PDFNet Licensing Linenumber : 0
Webviewer version 8 and we are using laravel framework.

Other files are opening without error.

So DOCX files open fine?

Platform : Linux Architecture : AMD64

The exception message is from Linux platform.

Are you trying to convert server side on a Linux OS?
Or are you using WebViewer Server?

Perhaps you could provide a screenshot showing the application reporting the exception so I have this extra context.