Unable to push to nuget feed (on prem) after last update

Hi,

I upgraded our TeamCity server (on prem) earlier today, and now we're unable to push packages to our nuget feed. We're not getting any errors, “dotnet push” hits the 5 minutes timeout.

Setting “debug-all” gives me the following information in teamcity-nuget.log:

[2024-04-02 11:07:47,284]  DEBUG - rs.upload.PackageUploadHandler - NuGet package upload handler has started
[2024-04-02 11:07:47,294]  DEBUG - x.NuGetPackageStructureVisitor - Nuspec file found on path Service.nuspec in NuGet package

Teamcity-server.log:

[2024-04-02 11:07:47,280]  DEBUG - ver.web.ResponseFragmentFilter - Request started: 15add0c9/76a8ad98 PUT http://localhost:8080/guestAuth/app/nuget/feed/_Root/default/v2/
[2024-04-02 11:07:47,280]   INFO -   jetbrains.buildServer.SERVER - Unexpected authority holder NO_PERMISSIONS_AUTHORITY found while pre-handling request PUT '/guestAuth/app/nuget/feed/_Root/default/v2/', from client 127.0.0.1:61313, user-agent "NuGet xplat/6.8.0 (Microsoft Windows 10.0.20348)", no auth

And the build agent gives me nothing of value:

[2024-04-02 10:42:37,112]   INFO - ----------------------------------------- [ Step 8/14: 'Push Service nupkg to NuGet server (.NET)' (dotnet), Build "Service / Build and package application" #356 {id=34407, buildTypeId='Service_BuildAndPublishToNugetServer'} ] -----------------------------------------
[2024-04-02 10:42:37,116]   INFO - Starting "C:\Program Files\dotnet\dotnet.exe --version" in directory "C:\BuildAgent2\BuildAgent\work\e7dee6bd35cc69e4"
[2024-04-02 10:42:37,272]   INFO - Process exited with code 0
[2024-04-02 10:42:37,279]   INFO - Starting "C:\Program Files\dotnet\dotnet.exe nuget push C:\BuildAgent2\BuildAgent\work\e7dee6bd35cc69e4\.\servicenuget\Service.nupkg --api-key ******* --source http://localhost:8080/guestAuth/app/nuget/feed/_Root/default/v2 --force-english-output" in directory "C:\BuildAgent2\BuildAgent\work\e7dee6bd35cc69e4"
[2024-04-02 10:42:37,285]   INFO - Starting: [30;1m.NET SDK 8.0.101 [0m"C:\Program Files\dotnet\dotnet.exe" nuget push C:\BuildAgent2\BuildAgent\work\e7dee6bd35cc69e4\.\servicenuget\Service.nupkg --api-key ******* --source http://localhost:8080/guestAuth/app/nuget/feed/_Root/default/v2 --force-english-output
[2024-04-02 10:42:37,290]   INFO - in directory: C:\BuildAgent2\BuildAgent\work\e7dee6bd35cc69e4
[2024-04-02 10:42:37,634]   INFO - Pushing Service.nupkg to 'http://localhost:8080/guestAuth/app/nuget/feed/_Root/default/v2'...
[2024-04-02 10:42:37,637]   INFO - warn : You are running the 'push' operation with an 'HTTP' source, 'http://localhost:8080/guestAuth/app/nuget/feed/_Root/default/v2/'. Non-HTTPS access will be removed in a future version. Consider migrating to an 'HTTPS' source.
[2024-04-02 10:42:37,652]   INFO -   PUT http://localhost:8080/guestAuth/app/nuget/feed/_Root/default/v2/
[2024-04-02 10:47:37,673]   INFO - 
[2024-04-02 10:47:37,674]   INFO - 
[2024-04-02 10:47:37,674]   INFO - Usage: dotnet nuget push [arguments] [options]
[2024-04-02 10:47:37,675]   INFO - 
[2024-04-02 10:47:37,675]   INFO - Arguments:

As you can see, it waits about 5 minutes and then we get the help section for dotnet.

One of the builds managed to push the nuget package after we restarted the entire server, though now no-one works.

I am able to surf to the nuget feed (getting XML data, etc) so the feed is responsive. But it's not accepting anything through PUT.
I am completely flabbergasted on what could be the issue. Any tips?

Thanks!