Popular video conferencing platform Zoom encountered widespread outages Monday during the first day of school as students scrambled to log in to courses remotely.

“We have identified the issue causing users to be unable to authenticate to the Zoom website (zoom.us) and unable to start and join Zoom Meetings and Webinars, and we are working on a fix for this issue,” the video calling giant said on its website.

The problems started early Monday Eastern Time and later spread. Technical issues were reported across the U.S., with the most on the East Coast. Users in Canada and Europe also reported disruptions, according to outage tracking website downdetector.com.

Downdetector.com showed there were over 16,000 incidents Monday morning of people reporting issues with Zoom. Issues included trouble logging in, joining a conference or connecting with the server, the website showed.

Zoom said the issues were resolved around noon without providing details on the cause of outages. The company’s shares fell as much as 5.4% on Nasdaq Monday morning. The stock has surged more than eight-fold since its initial public offering last year and four-fold so far in 2020.

The San Jose, California-based company, has become a main platform for people to join online meetings, classes and social events as the Covid-19 pandemic forced people to stay home. Zoom had 300 million daily meeting participants in April, according to the company’s latest disclosure.

Contact reporter Han Wei (weihan@caixin.com) and editor Bob Simison (bobsimison@caixin.com).