Have just bought AVG Internet Security 2017 but it won't install?

Hello Katie,
I'm sorry to hear that you're experiencing issue with AVG installation. I have sent you an email, please follow the email instruction to connect with us remotely. We will check with your installed AVG program and we will help you to install AVG Internet Security.
Best regards,
Alok.

I had the free version which I uninstalled but when installing the above it keeps failing and saying this error code
Description: General error (0x0783)
Error code: 0xC0070783

What am I doing wrong?
Hello Katie,
I'm sorry to hear that you're experiencing issue with AVG installation. I have sent you an email, please follow the email instruction to connect with us remotely. We will check with your installed AVG program and we will help you to install AVG Internet Security.
Best regards,
Alok.