Their site's news section has updates on this topic (with especially relevant passages highlighted by me for emphasis):

9/29 Update: Several local and regional USPS depots were apparently flooded with priority bins over the weekend and have a huge backlog pending scan, however we are being told they are catching up so we're looking to see if all remaining/unscanned packages finally get their scans by tonight. At this point about 95% of packages have scans or are delivered so we're down to the last few. If you still don't see anything on your package by Wednesday night let us know. Also on average we're seeing about a 1.3 day delay for transit meaning if you usually you got yours in 2 business days for this batch you're probably looking at 3 or 4 days.

9/25 Update: As previously alerted, ZNR Draft, Collector and Set boosters were only partially shipped by Wizards, and Bundles were not shipped at all. So if your order is missing any of those items they will automatically ship when the units arrive to us from Wizards, which is currently projected to be within the next 1-2 weeks. We will post any changes or other alerts here. Also of note is that carriers are still significantly behind so please allow till Tuesday or Wednesday before contacting us if regarding (receiving no items at all, not even partials). Please note that if you contact us asking where missing contents are, we will refer you to this article and the Wizards article linked below as we don't have any other information beyond this at this time and every minute spared is another shipment that can get out the door during this extremely high-volume and covid-complicated product release period.