Maduro just responded to a journalist from the Washington Post that they will not be able to show the local vote tallies now because, at this moment, the National Electoral Council is in “a cyber battle never seen before.”
And the website is currently not loading. They might simply be struggling to keep up with traffic, but being under some kind of "cyber attack" is also plausible
Simply give a ballot to every voter and have them fill it out. Especially nowadays, as pretty much every election in every nation will come under cyber attack precisely because they are using electronic voting and hackers can manipulate the votes.
If I were being ungenerous, I would say all the politicians want electronic voting everywhere because they can manipulate it with cyber attacks.
In this case I would say the simpler assumptions are just that they did steal the election and that the website is down due to global traffic.