If you use a legacy version of the product (a version prior to 10.2), you have to upgrade your version to 11.0 and then to version 12.80 or 12.71 before you can upgrade it to version 12.80.
We recommend that you contact our Customer Care team for assistance –
https://support.smartbear.com/message/?prod=QAComplete
After you upgrade your product version to version 12.80 or 12.71, follow the instruction to upgrade it to version 12.84.