How to create a new issue?

Hello,
I'm using version 2019.2.0 on a version on a 2019.2 server and I want to create a new issue.
This is my code:
```c#
BearerTokenConnection connection = new BearerTokenConnection(
"https://youtrack.example.com/",
"perm:Ym...Dfg");

IIssuesService issuesService = connection.CreateIssuesService();

YouTrackSharp.Issues.Issue ytIssue = new YouTrackSharp.Issues.Issue
{
Summary = summary,
Description = descriptionBuilder.ToString(),
};

string ytIssueID = await issuesService.CreateIssue("SIMNC", ytIssue);
```
During the call to `CreateIssue` my program just ends without any error message and the issue is not created.
What am I doing wrong?