There are several reasons why you may encounter this error:
The exchange rate has changed between the time you entered the amount and the time you clicked "Swap Tokens";
There is not enough ETH or BNB or MATIC in your wallet to pay gas fees. You will need approximately .06 ETH / .03 BNB / .02 MATIC / .01 Optimism/Arbitrum/Base ETH / .01 AVAX / .01 xDAI, .01 FTM, .001 Aurora ETH, or .01 KLAY to cover potential gas costs (this entire amount might not be used, but is needed to ensure total coverage of gas fees);
The assets you are trying to swap are highly volatile and/or there is low-liquidity in the pool. To account for this, you will need to increase the slippage tolerance incrementally until the error message no longer appears.
***Please note: Increasing the slippage tolerance also increases the risk of front-running attacks. If you reach the max (49%), and are still seeing the error, something else is likely causing the issue.
If it is an ERC20 token with internal commission, then try enabling the "Compatibility Mode" button in the swap settings.
The token creator may have placed a restriction on selling, preventing the token from being swapped (this is often a sign of a 'honeypot' scam, but not always)
If you are still unable to swap the token after exploring these above solutions, there is a chance that the token's internal commission is too high to be routed through multiple liquidity sources. In this case, it is recommended to swap direct through the pool itself (not through 1inch Network).