The Constitution does not forbid it, and the VP need not budge unless and until moved to do so.
The power to certify the tally is said to be merely ministerial, but I think that is only because egregious stank like we saw arise out of PA, MI, WI and GA in November, 2020 has never been matched with a sufficiently masculinr VP possessing righteous anger and a concomitant willingness to devise and take proportionate action to save our country, non-VP critics be damned.
Alternative Slates of Electors would have had to be prepared by the state legislatures in question. They had abdicated or even legislated their procedural roles away to state SOSs or Governors.
Please cite any part of the Constitution that mentions, or even suggests, Congress "certifying" anything.