According to the 12th Amendment,

... The President of the Senate shall, in the presence of the Senate and House of Representatives, open all the certificates and the votes shall then be counted; ...

( https://constitution.congress.gov/constitution/amendment-12/ )

Vice President Pence did NOT open the certificates, someone else did it, violating the 12th Amendment of our very own Constitution.
The reason he was supposed to do this himself is a matter of trust, as he would be skilled enough to inspect each and every one of these certificates of vote as to it's authenticity, additionally, so one else slips another piece of paper in it's stead while he's not watching.

(Please find when these certificates are opened, I don't have the data package to review this.
Thanks. )

( https://www.c-span.org/video/?507663-4/joint-session-counting-electoral-college-ballots )