I had an approved 797 (TN) from a previous employer until Feb next year. I changed employers and got another TN which is valid until 2019 Dec. Since I lost the contract, I went ahead and found another contract whose TN expires in 2018. I am trying to get back to the company whose TN I have until 2019, but I read somewhere that only the latest I94 is valid. Is this true ? If I find a client can I go back to the TN that is valid till the end of 2019 ? Thanks.