Surface Pro 9 won't enter tablet mode after disconnecting the type cover

So it's been two days of back and forward with customer support and cannot get a resolution on this issue. Bought a brand new Surface Pro 9 and out of the box have had issues with basic functionality. Initially we thought that the auto rotation was janky but eventually discovered that we could boot up the device without keyboard attached and tablet mode worked great, but once we connected the type cover keyboard and then removed it, the device stays in desktop mode. I've reinstalled a fresh version of the OS three times, run all Windows updates, downloaded and installed the Surface Pro 9 drivers from the Microsoft site, done the 20 second power down... none of it makes any difference.

Anyone have any advice? If I can't solve this I will need to return and repurchase etc, which means I may just go elsewhere, this has been a pretty poor user experience and I was pretty excited for this purchase. Hoping to get some help, much appreciated 🙏