Snapchat is having a tough week. The company’s shares were downgraded Friday, the second time this week.

On Monday, Snap’s parent company was downgraded by Morgan Stanley, which was the underwriter for Snapchat's initial public offering. Now, analysts at Cowen lowered their rating to market perform from outperform, according to CNBC. The analysts also slashed their price target from $21 to $17 a share.

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An analyst at Cowen, John Blackledge, said Snapchat’s downgrade was due to a lower ad sales forecast.

The analyst wrote:

“We cut our '17-'22 ad revenue forecast given the competitive environment within Digital advertising and new monetization efforts like Direct Response and Self Serve, which are ramping in 2H17 and into 2018, likely taking longer to play out.”

Blackledge was also skeptical about Snap’s user growth, saying it’s not "slam dunk, particularly with other players with more scale, like FB and particularly Instagram Stories, competing for users and their finite time."

The analyst added:

"Lastly on the monetization front, it remains extremely early days as SNAP really only started to monetize its user base in '15/'16 mostly in the US, while many of SNAP's European/ROW offices opened in late '16 and early '17.”

The company’s IPO on March 1 was at $17, the largest IPO in the U.S. since Alibaba. On March 2, shares went up 44 percent, a $24.48 value, and the next day the stock hit its high at $29.44. On Monday, Snap shares plunged to a $16.95 low before closing down 1.1 percent at $16.99. As of Friday afternoon, Snap’s stock was at $15.30 after closing at $15.69 on Thursday.

Earlier this week Morgan Stanley said it was wrong about Snapchat’s stock.

"We have been wrong about Snap's ability to innovate and improve its ad product this year (improving scalability, targeting, measurability, etc.) and user monetization,” wrote Morgan Stanley analyst Brian Nowak. “Snap's ad product is not evolving/improving as quickly as we expected and Instagram competition is increasing."

Read: Is Facebook Copying Snapchat Features Like Stories, Filters? Messenger Boss Says No

Snapchat Struggling With Rivals That Copy It

Skeptics have been weary about Snap’s slow growth in daily active users (DAUs) and reported earnings. The platform is competing with bigger platforms, like Facebook and Instagram. Snapchat is also continuously trying to update its features, as other social media apps copy its functions. While Snapchat is known for its 24-hour disappearing stories, Instagram and Facebook have mimicked the app with their own stories feature.

Snapchat recently came out with multiple updates. The platform now allows user to post links to their stories, which is similar to how it works on Instagram stories, but on that platform the person has a verified account to do so. That feature could put Snapchat ahead of Instagram, since it’s not limited to only some people. The update also allows users to create backdrops for their stories, and lets them use different voice filters, without the need of visual AR lenses.