Where the Request Failed
NuGet blocked the configured feed because its service index or advertised resources use insecure HTTP instead of HTTPS by default.
NuGet is telling you the request failed before it got a clean response back. Treat the connection path and the failing environment as the first suspects, not the package or image name.
Restore connectivity to the package source
Switch the feed URL to HTTPS (recommended).
If you must use HTTP, set allowInsecureConnections=true for that source in NuGet.Config and document the risk.
Retry restore:dotnet restore
Validation
Re-run the failing command and confirm the original code/message is gone, and confirm expected artifacts or outputs exist (packages restored, build/publish succeeds).
Why It Happens
Usually this comes down to source URL is http:// instead of https://, a proxy or rewrite causes the service index to advertise HTTP endpoints, or legacy NuGet.Config still contains HTTP feeds.
Prove the Failing Environment Can Reach It
dotnet restore completes without NU1302.
Verbose logs show HTTPS endpoints, or explicit allowInsecureConnections for the source.
Mechanism
This is the part worth understanding if the quick fix did not hold. It explains what NuGet is trying to do at the moment the error appears.
NuGet treats HTTP endpoints as insecure by default.
If a source’s service index (or its resources) is HTTP, NuGet raises NU1302 unless allowInsecureConnections=true.
Examples
error NU1302: You are using a NuGet source 'MyFeed' that contains an 'HTTP' service index resource endpoint: 'http://example/v3/index.json'.Prevent Repeat Connectivity Failures
To prevent this, enforce HTTPS-only feeds via policy and config review, and audit NuGet.Config changes in CI.
Docs and source code
NuGet.Protocol insecure HTTP message
Message instructs allowInsecureConnections or HTTPS migration. - GitHub
<data name="Error_Insecure_HTTP" xml:space="preserve">
<value>You are using a NuGet source '{0}' that contains an 'HTTP' service index resource endpoint: '{1}'. This is insecure and not recommended. To allow HTTP resources, you must explicitly set 'allowInsecureConnections' to true in your NuGet.Config file. For more information, visit https://aka.ms/nuget-https-everywhere.</value>
<comment>0 - NuGet Package source url
1- resource endpoint url</comment>
</data>
<data name="Error_Invalid_package_id" xml:space="preserve">