Hello Cookie,
I understand the inconvenience.
There is no free version available for AVG PC TuneUp whereas you can download and install the trial version which is valid for few days.
Share the (screenshot) of message that appeared while installing PC TuneUp from AVG Antivirus interface.
You can post the screenshot here in your topic. Click on 'Answer' & then click on the 'Image' [mountain symbol] & follow the instructions.
To install the trial version of AVG PC TuneUp, visit this website: https://www.avg.com/download.prd-tuh .