Have just bought an Octavia with the Columbus Rns 510 DAB+ Sat Nav but the CD Multichanger is not being recognised. 

 The Multichanger will load and eject CDs

Thanks in advanced for any helpful advice or comments.

The Columbus has a multichanger built in that's why it won't recognise the external one.

2 hours ago, Simon TDI Sport said:

The Columbus has a multichanger built in that's why it won't recognise the external one.

The Columbus has a single DVD drive not a multichanger. It's entirely possible to have the Columbus with a cd changer, but it's also likely that the Columbus was added as an aftermarket by someone, and they didn't code things properly.

Many thanks Simon TDI Sport and Rustynuts for your helpful comments.