....The complication with this case is for some arcane reason the PA legislature takes the month of December off and they will have to call a special session to make this happen.
They made it happen for past session.
My guess.
If the legislature does not pass judgement on the electors, they pass zero electors to Congress and pass their resolution/opinion (complete)
Imagine you are a state rep. and must decide to certify elections/electors or not. There will certainly be immense pressure and/or resistance to overturn the vote in which roughly half of your constituents will hate your guts no matter how you choose. It will require guts and a backbone.
Some swing states may disagree on the slate of electors and send an R slate AND a D slate, in which case none are accepted by congress...which leads to neither Biden nor Trump with the magic 270. Which leads to each state's congressional delegations casting 1 vote...Rs win 26 to 23/24.