I noticed that the latest Proget version has a v3 connector for nuget so I added that and also re-indexed the package store, recomputed the checksums and deleted invalid packages. While running the re-indexing I encountered three errors that indicated bad packages (files in use), so I deleted all three packages, ran the re-indexing and everything appears to be working again. I suspect the problem was the bad packages in the store.

Thank you @atripp for your help in this matter.

I did that but the pass through still seems broken. I also tried re-indexing the symbol server but that didn't make a difference either.

Is there a way to roll back to version 5.2? When I tried uninstalling and reinstalling Proget it wiped all of my settings and seemed to get hung up on the sql database. I think it didn't like that I had existing feeds.

@atripp So, I was just checking my credentials on nuget.org and found this disclaimer:
NuGet.org password login is no longer supported. Please use a Microsoft account to sign into NuGet gallery.
The connector uses a username/password. Should I change this to my ms credentials?

@atripp I just noticed out yarn feed seems to be pulling in packages just fine.

Something else I tried was changing the nuget connector to the v3 api but that doesn't seem to have made a difference.

@atripp This has been happening since last friday. Old packages that are already in cache work fine. New packages are not pulling from nuget.org.

An example from this morning: Our build requires Microsoft.EntityFrameworkCore.Analyzers 3.1.3 but when I look at the files in ProGet, the latest version listed is 3.1.2 and it will not pull 3.1.3 automatically. However, if I manually add version 3.1.3 through the proget ui, the build passes that restore and fails on the next NEW package.

Our nuget.config is:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <solution>
    <add key="disableSourceControlIntegration" value="true" />
  </solution>
  <packageSources>
    <add key="ProGet" value="https://proget.bowl.com/nuget/Nuget/" />
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
  </packageSources>
  <config>
    <add key="DefaultPushSource" value="https://proget.bowl.com/nuget/Nuget/" />
  </config>
</configuration>

I added the nuget.org package source this morning and the build completes now but it kind of defeats the purpose of proget as it's bypassing our local source when it can't find a package. The build completed but Proget still does not list 3.1.3 for Microsoft.EntityFrameworkCore.Analyzers

I'm not sure exactly when this started but the pass through to nuget.org to pick up new packages seems to be broken.

C:\Program Files\dotnet\sdk\3.1.201\NuGet.targets(124,5): error : The feed 'repositoryPath [https://proget.bowl.com/nuget/Nuget/]' lists package 'Microsoft.EntityFrameworkCore.3.1.3' but multiple attempts to download the nupkg have failed. The feed is either invalid or required packages were removed while the current operation was in progress. Verify the package exists on the feed and try again. [E:\Build021_work\364\s\ResourceAccess\Setup\Usbc.ResourceAccess.Setup.Fabric.Host\Usbc.ResourceAccess.Setup.Fabric.Host.csproj]
C:\Program Files\dotnet\sdk\3.1.201\NuGet.targets(124,5): error : Unable to find package 'Microsoft.EntityFrameworkCore.3.1.3'. [E:\Build021_work\364\s\ResourceAccess\Setup\Usbc.ResourceAccess.Setup.Fabric.Host\Usbc.ResourceAccess.Setup.Fabric.Host.csproj]

I can manually add the new packages to proget via nuget.org but automatically through the build process is broken.

I suspect it started happening with version 5.3 but I'm not sure.

I did try rolling back to the latest version 5.2.x but there's no downgrade path and manually uninstalling and reinstalling resulted in a sql error on the new install. Luckily I had a snapshot to fall back on.