knifing putty or substitute to repair leak metal water can (Hoddesdon EN11)

I have a tube however due to time kept in storage it no longer is able to be squeezed out of its tube. Please only offer putty or a suitable substitute if it is useable and functional, testing it if necessary. I was using 100g Holts Cataloy Knifing Putty -three-quarters left was unusable :(.