The law says what the process is on Jan 6. It is silent as to what happens if the process on Jan 6 is disrupted. There is no law that brings them back together,

The law says what the process is on Jan 6. It is silent as to what happens if the process on Jan 6 is disrupted. There is no law that brings them back together, so if they don’t finish their job on that day, they would have entered a Constitutional grey area, a kind of hack of the electoral process system. Trump needed such a hack because the regular order would have, and did, end with him losing power. This is why Pence refused to leave the Capitol, McConnell insisted on finishing the certification that night, and Trump’s associates were furiously calling Senators to continue delaying the certification (even after the insurrection).