As the Associated Press reported:

U.S. Sen. Joe Manchin is the only Democratic senator who did not co-sponsor an LGBT anti-discrimination bill.

The Register-Herald reports 44 Democratic U.S. senators and the two independent senators that caucus with them have signed onto Senate bill 788. The bill sponsored by U.S. Sen. Jeff Merkley of Oregon would add LGBT protections to the Civil Rights Act of 1964 and the Fair Housing Act of 1968.

Manchin did not sponsor a similar proposal in 2017. A spokeswoman for his office declined to comment to the newspaper.

Yesterday, Manchin explained why:

I strongly support equality for all people and do not tolerate discrimination of any kind, but I am not convinced that the Equality Act as written provides sufficient guidance to the local officials who will be responsible for implementing it. MORE: https://t.co/Q9xf2Yn8wv

— Senator Joe Manchin (@Sen_JoeManchin) March 18, 2019

Also yesterday: the state Democratic Party asked Manchin to support the legislation.

I searched but could not find what the senator thinks is "sufficient guidance to the local officials." Perhaps the senator simply didn't want to upset Eric Porterfield's (R - Mercer) supporters because you never know when you might need their support.