In a test, these are the messages spewed when inserting an (ext2) formatted SD card into an already up & running plug:
error -110 whilst initialising SD card
mmc0: error -110 whilst initialising SD card
mmc0: error -110 whilst initialising SD card
mmc0: error -110 whilst initialising SD card
mmc0: error -110 whilst initialising SD card
mmc0: error -110 whilst initialising SD card
mmc0: error -110 whilst initialising SD card
mmc0: error -84 whilst initialising SD card
Once it settles down (around 5 seconds), mounting becomes possible:
mkdir /mnt/sd-test
mount /dev/mmcblk0p1 /mnt/sd-test
After unmounting and removing the card, the mmc0: error -110 (etc) error messages are
not re-sent, and re-mounting is again straightforward.
I don't have any blank / unformatted cards here right now, so I can't test for "normal" messages in response to insertion of such a card.
If your plug consistently refuses to recognise any SD cards, write to
sales@newit.co.uk and tell us the serial number of your plug and the models of cards that you have tested, what procedures you have used, and how you are trying to mount the card (you can use my example as a test that ought to work -
/dev/mmcblk0p1 is partition #1 on an SD card and
/dev/mmcblk0p2 is partition #2 (etc).