Trump and JD to refuse to certify the 2028 election and claim it was rigged, what happens next?

The democratic nominee won 300 electoral votes where as JD vance (running for the Republican party) only got 238 electoral votes.

The Republicans have a majority in the house of representatives and believe JD vance won and say the election was rigged.

The election wasn't rigged and there is no evidence of this.

What happens.