What happens when you download?
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Thanks Pete.Green. The blog post worked for me. All upgraded.
It downloaded as normal. Replaced 5.6 with 5.7. I opened Lightroom & all is fine. No problem. For some reason earlier when I opened Lightroom & the dialogue box informed me there was an upgrade & click here if you want it, when I clicked, nothing happened (twice). Glitch. Resolved by following your advise.