Hi Gary /
@Babine
I don't use Windows machines anymore yet here is what I have found:
You need to make sure in PS Settings that you are saving previews:
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You need to make sure you have the correct settings in Windows Explorer
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There is another setting in Windows that likely is not it yet its possible:
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Lastly, all the plugins have file size limitations (or speed issues) in the generation of Thumbnails. You can test the plugin with a small PSD to identify if that is the problem or not:
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More choices out there than I new about.
Of course, make sure you turn off PS and reboot windows as well as some things don't take effect unless you do.
Not sure this solves the root cause issue yet thought it was worth sharing
John Wheeler