'System.Net.Http.HttpRequestException: No such host is known' error after deploying

I am writing a blazor server side application (.NET6) for my homeautomation and let it run on iis on a home server.

If I run the following code on my local machine in IIS Express everything works fine.

string _urlForecast = "https://api.openweathermap.org/data/2.5/forecast?id=...";
Uri myUri = new Uri(_urlForecast, UriKind.Absolute);
HttpResponseMessage response = await HttpClient.GetAsync(myUri);
var data = await response.Content.ReadAsStringAsync()

If I deploy it to my local homeserver and run it I get the following error:

System.Net.Http.HttpRequestException: No such host is known. (api.openweathermap.org:443)

My 'homeserver' is also running windows 10 and is in the same network as my dev pc. It is in the same ip range and has the same DNS settings on the network adapter. I also tried it with turned off firewall with the same result. I am injecting the httpClient with DI but also tried without DI. I tried to use http://api... and https://api... as my application is also available in the internal network via https. Unfortunately I have don't have any experience with Http requests and would be thankful if anybody could help.