Palantir shares opened at $10 on the New York Stock Exchange. Existing investors are allowed to sell up to 20% of their shares before the lockup expires. But several former workers, who asked not to be named because they weren't authorized to speak to the public, told CNBC that they and some current employees couldn't get into Morgan Stanley's Shareworks system.
The stock traded as high as $11.42 before closing at $9.50. Current and former employees were texting with each other about the problem and complaining of their inability to sell. One former employee followed up with CNBC to say the system finally started working late in the morning, Pacific Time.
Palantir, which makes data analysis software for government agencies and big corporations, debuted on the New York Stock Exchange with a direct listing instead of a traditional IPO. One of the benefits is that existing investors can sell some shares rather than waiting for a typical 180-day lockup to expire.
Palantir didn't respond to a request for comment. After publication of the story, a spokesperson for Morgan Stanley's Shareworks group sent the following statement:
"We experienced slowness that may have resulted in delayed logins into our system. At all times our call centers were available to execute trades. We will work through any issue that is brought to our attention and ensure that no employee will be disadvantaged."
— CNBC's Leslie Picker contributed to this report.