Using an old agent version is a potential source for a range of unexpected issues on your apps which otherwise might have already been fixed in newer versions.
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Therefore, it is required that you update your apps periodically to use our latest agents version.
this This article describes how to make it happen.
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Pls follow Downloading the .NET agent files
Note: If you download the agents/plugin from an internal repo, you must make sure the updated version does exist there before changing the version number