Normal shelf life is about 5 years when stored below 25 deg C.

Please have a look right to the bottom of the can and see if resin has separated there due to high temperatures and/or vibration from transportation in a truck or car etc.
Your description of “kind of porous” sounds as if the lightweight components have floated up to form a crust on the surface. With the high summer temperatures this year we have seen a few cases of this in Australia.

You do have the red hardener supplied with every can I assume, and used this to catalyse the hardening reaction?. I ask because the fill should be pink and not look at all like plaster.
Please let me know how you get on and email me the batch number on the small white sticker under the plastic overcap if you have further concerns.

Regards
Stuart Jordan
Managing Director
(26.3.2020)