The second landlord and the big landlord transferred the store after the contract expired. What should I do?

The contract is valid. The contract is only binding on both parties. You can ask the second landlord to bear the liability for breach of contract according to the contract, but you can't ask the big landlord to rent it to you.

According to the law, if the lessee (second landlord) subleases the leased property to a third party with the consent of the lessor (big landlord), and the sublease term exceeds the remaining lease term of the lessee, the agreement on the excess part is not legally binding on the lessor unless otherwise agreed by the lessor and the lessee.

If you want to restrain the second landlord, you can increase the liquidated damages, but if you want to continue to rent the second landlord when the remaining lease expires, there is nothing you can do. When you sign the sublease contract, you must see how long the remaining lease period is. It is suggested to sign a lease contract directly with the big landlord.