To comply with the terms of the Byrd Rule that allows Senate Republicans to bypass a Democratic filibuster, the tax plan must meet two conditions. On the one hand, it needs to comply with the budget resolution's mandate to raise the deficit by no more than $1.5 trillion over 10 years. According to Penn-Wharton, it does that. But on the other hand, it needs to not increase the long-term deficit in the years following.
And here's where Penn-Wharton says that there's a problem: "We estimate that the Senate TCJA continues to reduce revenue in years beyond the 10-year budget window."
Critically, this conclusion does not change when they attempt a "dynamic" score that considers the potential growth-boosting effects of tax cuts. Instead, they find that "the Senate Tax Cuts and Jobs Act reduces federal tax revenue in both the short- and long-run relative to current policy. In the near term, there is a small boost to GDP, but that increase diminishes over time."