This usually means a fitting, a seal, or the brine tank rather than the resin inside.

The bypass o-rings, the drain elbow, and the brine line are the parts that move or get handled, so they are the ones that usually give up first. The tank itself rarely splits.

Find the wet spot when the unit is idle, then look again during a regeneration. Water only while it cycles usually points at the drain line or the valve. Water all the time usually points at the bypass or an inlet fitting.

Do not buy a replacement softener on the strength of a puddle. Most leaks here are a seal or a fitting, and swapping the whole unit for one of those is an expensive way to change an o-ring.