Sellers, who pay Amazon a fee to sell products on its site, had been unable to change prices or let customers know an item had been sold out, among other problems.
Amazon had said it was conducting "maintenance," but did not say why, or why sellers were experiencing problems, until Saturday.
"Maintenance is now complete; full seller account functionality has been restored for all sellers," the company said.
Amazon initiated theas part of an effort to add its Marketplace feature to its sites in Germany and the United Kingdom, said company spokeswoman Carrie Peters.
Like eBay and Yahoo, Amazon allows individuals and companies to set up virtual stores on its Web site. Sellers can offer products through these storefronts, called zShops, or through Amazon's product pages in a feature called Marketplace. Problems hit both zShops and Marketplace.
Amazon generally charges sellers $39.99 each month to list an unlimited number of Marketplace items and up to 40,000 items in an auction or in a zShops storefront. The company also charges a commission fee on each sale that varies depending on what area of the site it was made in.
The work was an attempt to "increase capacity," Peters said, but she declined to explain.
"Overwhelming demand (on the European sites) caused some unexpected delays in our efforts to restore functionality. Some sellers were unable to access portions of their accounts," Peters said. "We appreciate their patience."
Peters declined to give more details on the source of the problems.
Amazon initially announced that it would be doing some "planned maintenance" on its zShops storefronts and Marketplace on March 18. As a result, sellers were unable to edit, delete or update their storefronts listings directly on Amazon's site. Meanwhile, items listed on Marketplace weren't showing up on zShops.
Amazon waited more than 10 days to explain to sellers why it was doing the maintenance or why the maintenance was causing problems.
But those problems have now been fixed, Peters said.
Many sellers said that their sales plummeted during the last two weeks. One bookseller in Missouri, for instance, said his sales dropped from 10 to 15 books per day through Amazon to just one or two.
"I'm not happy about it, but I'm sure Amazon's not happy about it either," said the bookseller, who asked that his name not be used. "I'm just hoping they have resolved their problem."
The bookseller said that Amazon offered him a $10 rebate off his monthly fees. Peters declined to confirm or deny whether the company was offering rebates to all or a portion of its sellers.