Orders that are not paid within 72 hours may be canceled by Reverb. Buyers who repeatedly do not pay may be subject to account suspension.

Once paid, the seller is required to supply a tracking number to the order within 3 business days, at which point you'll receive an email notification with a link to track your package.

If you have an unpaid order you need to submit payment for, just head to your Purchases page in the "Buying" section of your Reverb account, or click on your Unpaid Orders notification in the upper right-hand corner of the site.

Further reading:
How do offers work on Reverb?
How do I cancel an order?
Can an offer be canceled?
My payment is processing, what does that mean?
I have several items in my Cart but I can't seem to check out all at once