Not quite a source on that exact statement, but here.Got a source on that?
The expanded Child Tax Credit expired in January 2022. When the Build Back Better Act was in negotiation, Joe Manchin said he would not support it unless the CTC element included a stipulation that recipients be working. It ended up being removed from the bill.
A lot of people have accused Biden of retreating too easily, being too willing to drop it, or using the Manchin vote as an excuse to do so. And TBH their scepticism is pretty justified.
Biden has however included a reinstatement of the CTC expansion in his 2025 budget.