...and it stopped working again.
I visited the MS store in Sydney and they ran several diagnostics which simply confirmed that the typecover port wasn't working. The typecover itself is fine. They couldn't help further as the device is out of warranty.
The typecover has worked intermittently a couple of times since then, but not recently. I now also carry a bluetooth kb with me.
It also runs flat overnight despite configuring the power settings configured for decent battery life.
The device has been well cared for and is in otherwise excellent condition.
Perhaps they have actually properly investigated a failing unit and are unable to fix the defect.
Microsoft silence makes it difficult to recommend a surface device to anyone else.