IME, I judge it like this.

If the paint smells bad when it is opened, or even not like latex
(which should have a very slight to heavy ammonia smell) it goes out.

If there are any kind of lumps, skin, or dried rings inside the can.
It goes out. If there was any paint used out of the can, any at all,
it goes out.

I would open the can, inspect thoroughly, and have it professionally
remixed. The zinc solids will migrate to form a paste on the bottom
of the can. This paste can take forever to stir back in with a 1/2"
drill and the proper sized stirrer.

Test it on a board and see if it lays out. If it does, success!

Robert