Here’s the relevant section of the Constitution
https://www.archives.gov/founding-docs/constitution-transcript#toc-article-ii—2
And relevant Amendment
https://www.archives.gov/founding-docs/amendments-11-27#toc-amendment-xii
“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; — The person having the greatest number of votes for President, shall be the President, if such number be a majority of the whole number of Electors appointed; and if no person have such majority, then from the persons having the highest numbers not exceeding three on the list of those voted for as President, the House of Representatives shall choose immediately, by ballot, the President.”
Pence just opens the envelopes, he has no role in adjudicating anything.
Stop listening to blog pimps and read the Constitution.
You still have not shown me where it says “shall not” anywhere.