I have no idea if this is the problem or not (or even if this is still a problem), but somebody on another forum posted this:

Just heard from a tax preparer who received from an IRS employee a copy of an internal IRS memo revised 25 June which stated, “…accounts with Estimated Tax Payments…are temporarily being prevented from settling…, including refunds. A request has been submitted to release…refund and zero balance accounts to mitigate taxpayer hardship.”

Apparently, due to a glitch, refunds resulting from estimated payments (returns that would’ve been balance due returns without the estimated payments) will only be processed 17 August. She included an emoji of her hitting her head.