Site down following installation

I installed the Kommento package, attempting to upgrade. It took down my website http://www.rossmartin.co.uk
Do you have any ideas what settings you might have changed. I was already on PHP 7.1.25 and Joomla 3.9.1
I have now disabled Kommeno and this made no difference.
I have now restored the site and we are running again. I would like to use Kommento but I am now terrified of trying to install it. Would you be able to assist me?

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