Maybe you downloaded PhotoLab7_Setup.exe to the same directory as previous version,
so Windows saved it as “PhotoLab7_Setup (1).exe”, and then you executed the old exe?
Unfortunately DxO does not include full version in its setup filename.
The properties box shows 7.2 and it installs as 7.2 on my other computer
On the first computer, although the install process completes without error, the photolab.exe file still shows 7.1. However, other files in the same folder reflect the December date. So, something did install.