Facebook’s ad platform crashed for several hours Tuesday, just days ahead of Black Friday — one of the most important days of the year for both retailers and online merchants.

As Black Friday draws closer and retailers and online merchants prepare for one of the busiest shopping days of the year, both Facebook and Instagram’s advertising platforms went down, making it impossible for media buyers to run ads on the platforms. CNBC reports that ad buyers were unable to utilize Facebook and Instagram’s advertising analytics platform to view data about how ads were performing, edit current live ad campaigns, or create new ad campaigns.

“We’re aware that some people are currently having trouble accessing Ads Manager,” a Facebook spokesperson told CNBC in a statement. “We’re working to resolve the issue as soon as possible.” The issue reportedly persisted for up to eight hours, into Tuesday afternoon.

I've never seen it down for this long. 7 hours now. pic.twitter.com/yCOXpTYDLC — David Herrmann (@herrmanndigital) November 20, 2018

One media buyer stated that they had never seen glitches on the platform this bad, adding that if they were unable to place ads, it could seriously affect their sales as consumers would be unaware of sales or products being sold on Black Friday. Another buyer referred to the timing of the Facebook crash as “unfortunate,” and stated that it could leave all Facebook ad buyers rushing to update or create ad campaigns before Black Friday.

Black Friday and Cyber Monday are some of the biggest shopping days in the U.S. market, with the most recent Cyber Monday becoming the largest online shopping day in U.S. history, accounting for $6.59 billion in sales.