QB Issue Resolution:

Do you still have the backup copy of the QBW file created back in 2010? If yes, I suggest to re-convert the backup file. Once done, check if those invoices still show unpaid.

Resolution for Issue 'I upgraded to QB 2015 pro from 2010 pro. About 30 of my invoices that are more than a year and up to 4 years old are now appearing as unpaid. How can I fix this?' available: Yes (Solved).
Source: Intuit Community forum.

I upgraded to QB 2015 pro from 2010 pro. About 30 of my invoices that are more than a year and up to 4 years old are now appearing as unpaid. How can I fix this?: this issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for Invoice
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Error Recovery for Invoice [Canada]
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