The weight management firm's technical problems were particularly unfortunate as they coincided with Thanksgiving in the US, the company's home market.
The company said on Facebook: "We know many of you are counting on us today to help you through the food-filled holiday and we want you to know we are working to get this functionality to you as soon as possible."
The problem, which occurred on the Weight Watchers US website, saw the brand inundated on Twitter, and it replied with a generic message to users.
@jbquinn we are sorry for the inconvenience. We are aware of the issue and running an update to get it corrected shortly.— Weight Watchers (@WeightWatchers) November 26, 2015
Some customers were redirected to customer services support in their individual market, while on Facebook Weight Watchers posted an apology and directed customers to an online information page.
That page said that Weight Watchers had been undergoing significant digital transformation in recent weeks, and thanked users for feedback, saying: "Thank you so much for your detailed feedback over the past weeks! We are reading every message. However, due to the volume of messages, we might not be able to reply to every message we receive directly, but rest assured – we are listening. Please check back to this page often as new features become available."
PRWeek UK contacted the firm's new UK consumer PR agency, which provided a statement saying the brand was "excited to be launching our new digital innovation globally including upgrading our app and web technology", and that a "small percentage of our members have unfortunately experienced some issues". It ended: "As always we are here to help our members and support them and we are making contact with all those members that have been affected."