What it means
A token transfer OUT of the contract failed: the pool or vault tried to send you tokens and the token contract refused. Common with tokens that have transfer restrictions, fees on transfer, or paused states.
How to fix it
If this is a swap, try a smaller amount or a route that supports fee-on-transfer tokens. If it is a withdrawal, check whether the token or the protocol is paused before assuming your funds are affected: a revert means nothing moved.