Just Excluded From Fee Addresses Can Buy and Sell!

I have deployed a contract on bsc testnet and I am using this DEX which is simulating PancakeSwap on testnet.

My contract code:

But it seems that only excluded from fee wallets can buy and sell.
For the others I get this error:
The transaction cannot succeed due to error: undefined. This is probably an issue with one of the tokens you are swapping.
Could anyone help me please?