Here is a photo found on this site of a Seeeduino Stalker with a SD card fully inserted:
Here is my Stalker with the SD card pushed in as far as it will go
Is this SD card fully inserted?
I can read the same SD card with an arduino uno with card reader but not with the stalker with the same settings etc
The answer is the card is not fully inserted in the photo.
The SD card reader on this Stalker 3.1 can be opened by sliding the top forward and flipping it open. The SD card is then put into place and the top of the SD card reader is closed and locked.
Now working.
Thanks to Jiangli at Seeeduino support.