"My Slime arrived stiff"
Shipping in the cold weather will make your slime stiff let it sit in the container in a warm place for a couple of days to thaw out and it will be perfect and stretchy again :)
"My Slime Turned hard and is drying out"
When slime is exposed to air for an extended period of time from being outside of the container it will start to harden because slime is made with air dry glue. To fix this let the slime sit in the container for a couple of days to regain it's moisture if this doesn't work it might be time for a new slime.
"My Slime Turned hard when I added Activator"
Too much activator will make slime hard but this can easily be fixed by letting the slime sit inside of its container in a warm place for a couple of days it will melt back to normal and be stretchy again.