Can the IRS keep holding my tax return without cause? It’s been much longer than 21 days they accepted my return from Turbo Tax.

Turbo Tax checked my taxes and the It’s accepted them. It’s been past 21 days by 2 weeks now and all they will say is that it’s taking longer than normal to process. They aren’t saying there is anything wrong with the return just that it’s taking longer to process. What gives?!