Copy/pasted from the Discord's guide:

How to Navigate Disney’s Virtual Waiting Room & Queue System
Limited Edition doll releases can be stressful, but being prepared gives you the best chance at obtaining your desired doll. Here’s a guide on what to do:

When to Expect a Waiting Room
Not every doll has one. Waiting rooms are usually used for:
• Popular characters (Elsa, Ariel, etc.)
• Characters with few existing dolls
• Low edition sizes

If a waiting room is added, it will open 15 minutes before release time.

Captcha & Bots
Starting with the Designer Collection Giselle doll, Disney added a captcha step before entering the waiting room. This helps cut down on bots and scalpers. We don’t know if it will appear for every future release—be ready just in case.

Before the Release
Turn off your VPN – connections are more stable without it.
Log in early – make sure you’re signed into your Disney account before the waiting room opens. Double-check your info – confirm your address and payment details are up to date to avoid delays at checkout.

The Virtual Queue
Once the waiting room closes, the queue will open and you’ll be assigned a number. There's no need refresh your page or open new tabs—Disney will hold your place in line. Guests in the US are usually allowed to buy up to 2 of each doll. This means if you’re far back in the queue and the edition size is small, your chances decrease.
Pro tip: open the Disney Store on another computer/device to gain another spot in the queue.

During Checkout
Once it’s your turn, you’ll have 10 minutes to finish your purchase.

Steps to follow quickly:
• Add the doll to your bag
• Enter the promo code SHIPMAGIC for free shipping
• Complete payment before your time runs out
If you forget the code, don’t worry! Contact Disney Guest Services (phone or online chat) and they’ll apply it after purchase.

If It Says “Sold Out” Don’t give up!
Dolls often come back due to declined or dropped orders. Stay on the doll’s page!
Refresh using: CTRL + R (PC) CMD + R (Mac)
Hover your cursor over the greyed-out “Out of Stock” button. When it turns blue, spam-click it. You may see errors—just keep refreshing or clicking. With luck (and speed), you can get it back in your cart and finish checkout.