Amazon.com Inc’s marketing portal for merchants crashed Tuesday night (July 16), according to multiple Amazon sellers and consultants, fouling up one of the online retailer’s biggest sales of the year.

The advertising portal is a self-service system where merchants and brands can adjust their ad budgets and bid on key words so their products appear in response to consumer queries. Without that online interface, brands are flying blind with their ad spending on Amazon.

This year’s Prime Day sale, a two-day discounting spree, got off to a fast start Tuesday with sales up almost 12% in the first seven hours compared with the same period last year, according to Momentum Commerce, which manages 50 brands in a variety of product categories. It’s a crucial time for both Amazon and its sellers.

“A very small portion of advertisers have had limited access to the Amazon Ads console for a brief amount of time and we are already resolving the issue,” an Amazon spokesperson said in an emailed statement. “There is no impact to ad delivery and advertiser campaigns continue to run as they intended.”

Jed Rawson, whose consulting firm Pirawna manages Amazon accounts that sell nearly US$500mil per year on the site, said several sellers are discussing the issue online. All of his clients are affected and Bloomberg reviewed a private Slack channel of Amazon sellers in which four others reported having problems. Several Amazon consultants were also discussing the glitch on LinkedIn.

Rawson said the portal wasn’t functioning for about two hours before it was fixed. Amazon did not provide a time frame for the disruption.

 - Bloomberg