Windows Insider Program Get Started Button Greyed Out

I came across this because I wanted to make use of the new One-drive on demand sync feature which is only available if you run a Windows 10 insider version.

But the Insider program get started button was greyed out.

To correct this you have to set your privacy settings to "Full"
Settings > Privacy > Feedback & Diagnostics > Under "Diagnostic and usage data select "Full (Recommended)"

Also delete the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\DataCollection\AllowTelemetry

After a reboot you can finally join the insider preview program.