You were right. The US never rejoined.

Trump ordered the US to withdraw from the TPP because the partners refused to agree to one sided, anti-competitive, anti-consumer protections for US industry and a one sided, US centric dispute resolution process which the US would ignore when it lost.

The patnership is up and running and functioning as intended and US farmers continue to moan about the fact that they lost access to the TPP market. The Brookings Institute wrote an interesting article about it.