Error: Cannot declare class PDFGenerator, because the name is already in use

Hello, need help with the error below.

Ran the Blank page/500 error resolver with the following output:
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Ohhhh i found something, the invoice generation seems to be failing due this problem:
Error Message Cannot declare class PDFGenerator, because the name is already in use
Error Number 1
Error File /home/s1839/html/wp-content/plugins/woo-pdf-invoice-builder-pro/PDFGenerator.php
Error Line 23
Error Context “N/A”
Error Detail Unknown
If by seeing this error you know how to fix it GREAT!, if not please contact support including this information in your ticket =)
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Note: I had installed the free version initially then uninstalled it when I purchased and installed the pro version, don’t know if that has something to do with the class already being in use.