Just looked at source code and found this:
<b>Fatal error</b>: Uncaught ArgumentCountError: Too few arguments to function Jetpack_Photon::filter_srcset_array(), 1 passed in /var/sites/g/gucu.org.uk/public_html/wp-includes/class-wp-hook.php on line 298 and exactly 4 expected in /var/sites/g/gucu.org.uk/public_html/wp-content/plugins/jetpack/class.photon.php:629
Ouch
Anyone know what that means please?
Rich