• Amazon's website has been up and down since the start of Prime Day in the United States on Monday at 3 p.m. ET.
  • When it has been online, the website has been experiencing issues like links that appear to go nowhere, leaving customer unable to access the special deals.
  • Prime Day is one of Amazon's most important days of the year, when it hosts Black Friday-like deals in the middle of July.

Looks like Amazon wasn't primed for Prime Day this year.

Customers reported experiencing issues with the retailer's website at the same time as Prime Day deals were scheduled to begin in the United States, on Monday at 3 p.m. ET, with the site appearing to be down and responding with a 404 error.

While the homepage has been appearing as usual for some customers, many say the site still appears to be down.

When the site has been online, the links on the main page advertising Prime Day deals have gone nowhere but back to the page. Pages within Amazon's mobile app have also been affected, showing an error message with a photo of a dog.Individual product pages didn't appear to be affected and were still functional, though customers reported issues with adding items to their carts.

Customers reacted to the site issues with anger and confusion, with some even going as far as to threaten to cancel their Prime memberships. Many on social media posted pictures of the error pages with the dogs.

Amazon didn't immediately respond to Business Insider's request for comment on the site issues.

Prime Day is expected to be one of the biggest sales days of the year for Amazon. One Click Retail estimated that Amazon sells about $1 million a minute during peak time on Prime Day, based on last year's data. The issues this year could easily mean millions in lost sales, according to One Click Retail's founder, Spencer Millerberg.

At the time of writing, Amazon's website issues had lasted nearly an hour.

This post originally appeared on Business Insider.