It clumped or went sticky
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Where the water came from
Humidity in the room, a container opened repeatedly in a humid space, or cold stock brought into a warm room so that moisture condensed onto it. The last of those is the one people cause deliberately by freezing stock and taking it in and out.
In a tea blend, fruit is often the carrier
Dried fruit pieces hold more moisture than leaf does and can release it into a blend over time, producing stickiness that spreads. A blend that was stable as components and clumps when combined is usually telling you about one ingredient.
It is a quality failure before it is a safety one
Clumped product brews unevenly and looks wrong, which is enough to lose a customer. If moisture goes further than that, mold is possible in a product that should never support it, and that is a different and more serious conversation.
Check the lid, not just the container
Most moisture ingress in bulk storage is through a lid that is not actually closing. A gasketed lid left resting on top rather than secured is the single most common version, and it happens at busy counters.
Humidity in the storeroom is measurable
A cheap hygrometer tells you whether the room is the problem, which otherwise is pure speculation. It is the same category of instrument as a thermometer in an incubator: small, boring and it answers the question.
Do not dry it out and sell it
Product that has absorbed moisture has also undergone the chemistry that came with it. Drying recovers the appearance and not the quality, and it does not address mold if any has started.
Instant coffee is the extreme case
It is designed to dissolve, which means it takes up water from the air faster than anything else in this property and clumps into a solid block given the chance. If you handle it at all, it needs the tightest container you have and a lid that is closed the moment it is not in use.