SketchUp Make 2017 installation

Hi all,
I’ve successfully installed Sketch-Up Make 2017 on 16 PC’s this morning at a school but I’m getting an error when trying to install the last one.
It reads: ‘Account already exists’ when it’s trying to register the product. I’ve not done anything different and I’ve since installed it on other PC’s fine. There is no other version installed, and I’ve restarted the PC several times.
The PC in question is a Dell OptiPlex 3240 AIO all in one and I’ve been able to install the application on the other Dells just fine. Specs are:
Windows 7, 64 bit
i5-6500 3.2GHz
4GB RAM
2GB GPU
1920x1080
Any ideas?
Many thanks

Is the machine’s Windows Product ID unique ?
Is it’s Network MAC Address unique ?

If you installed this machine from a pre-setup disk image,
was mini-setup properly run so a unique machine SID was generated ?