Does the file you manually download have a digital signature tab if you view the properties of it?
You server is unable to verify the digital signature of the engines.manifest.cab file. It's possible the root certificate is out of date, you can update it using this site: How to get a Root Certificate update for Windows
Solved!! I had my server admin double check the root certificates on the site server and everything is fine after re-importing.
Glad to hear that.
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