The 409 Conflict status code can be returned because of several reasons:
The package size is too large for the current subscription. E.g. the Free plan only supports packages <= 100 MB. Check the package size and your subscription plan quota. When the feed owner created a private feed and you are on a plan that has lower quota, MyGet will apply your subscription quota. For example, when you are on the Free plan and are pushing packages to a private feed created by someone on a Starter plan, packages can still only be <= 100 MB.
The feed is over quota for the current subscription. Check the feed quota and your subscription plan quota.
You enabled any of the following package settings for your feed. Verify the package settings for the feed you are pushing to.Forbid overwriting of existing packages? - this will forbid overwriting packages that already exist on your feed (same package id and version)Forbid packages which are non-compliant with Semantic Version? - this will forbid uploading packages that are not compliant with Semantic Versioning. E.g. a package version like 126.96.36.199 will not be supported.
MyGet will return a detailed error when pushing packages with a full description of the issue. For some package managers, additional verbosity can be added (e.g. for NuGet use the -verbosity Detailed switch).