Sorry got cut off ....Can was in date but had been stored in a shed at +40 deg for ?months. The yeast failed. I saved the brew by adding US05 on day 4 or 5 which fermented fine. I don't use the yeast that comes with the cans anymore unless I'm sure it's been stored correctly.
As the others...
Leighton, I've only done a handful of brews so far but if it's any help to anyone I've had 2 issues so far that have been similar to your original post. First brew worked fine except fermenter didn't seal properly - so no bubbling. Fixed now by occasionally applying some food grade silicon...