Twitter shares tumbled more than 12 percent on Thursday after the social media platform disappointed investors with stagnant monthly active user growth in the second quarter.

Despite its appeal among celebrities and public figures, Twitter has struggled to sustain its closely watched user growth even as it invests in features and live content to help draw viewers and boost user engagement.

It is in stiff competition for advertising dollars with other platforms like larger rival Facebook and Snap Inc.’s messaging app Snapchat.

The company also reported a wider quarterly net loss and lower revenue, and said it did not expect its total revenue growth to pick up in the second half of the year.

Twitter had 328 million average monthly active users (MAU) in the three months through June 30, unchanged from the previous quarter. Analysts were expecting 328.8 million, according to financial data and analytics firm FactSet.

Shares had run up some 40 percent since mid-April as Twitter investors bet on another quarter of growth after the microblogging service reported adding 9 million more monthly active users than expected in the first quarter.

Twitter shares were off 12.8 percent at $17.09 in late-morning trades Thursday.

“If you really can’t accelerate MAU interest given the daily tweets from POTUS, not sure when you will,” said Michael Nathanson, senior research analyst of MoffettNathanson Research, referring to an acronym for the president of the United States.

President Donald Trump, one of the most active politicians on Twitter, has tweeted multiple times a day on average since his inauguration in January, according to social media analytics company Zoomph.

“The positive contributions to MAU growth from product improvements in the second quarter were offset by lower seasonal benefits and other factors, resulting in flat MAU quarter-over-quarter,” said chief operating officer Anthony Noto during a conference call with analysts.

In the United States, Twitter’s average monthly active users fell to 68 million from 70 million in the first quarter.

Monthly active users, a key performance indicator for social networking services, is typically calculated by tabulating the number of users who have logged in and logged out during the 30-day period.

Twitter’s shares fell as much as 14.1 percent at one point after the open to $16.85, wiping out about $2 billion in market value.

The company has been trying to boost revenue through livestreaming deals, but had a setback in April when it lost a deal to stream US National Football League games this year to Amazon.

Advertising revenue fell 8 percent to $489 million, but well exceeded the $458.1 million estimate.

Twitter’s net loss widened to $116.5 million, or 16 cents per share, in the second quarter ended June 30, from $107.2 million, or 15 cents per share, a year earlier.

Revenue fell to $573.9 million, the second time it has fallen since Twitter’s market debut in 2013.