Hi JOHNP,
You have javascript errors in your theme.
We improve the way to include scripts and styles in this new version but previous versions of some plugins aren't compatible.
You can try to update this plugins if there are compatibles with osclass 3.1 or you can change this 2 files:
You can edit your theme file functions.php
ROOT/oc-content/themes/modern/functions.php
At the end the file add this lines...
osc_remove_hook('header', 'osc_load_scripts');
osc_remove_hook('header', 'osc_load_styles');
osc_add_hook('header', 'osc_load_scripts', 4);
osc_add_hook('header', 'osc_load_styles', 4);
and for your oc-admin edit:
ROOT/oc-admin/themes/modern/functions.php
At the end the file add this lines...
osc_remove_hook('admin_header', 'admin_theme_js');
osc_remove_hook('admin_header', 'admin_theme_css');
osc_add_hook('admin_header', 'admin_theme_js', 4);
osc_add_hook('admin_header', 'admin_theme_css', 4);
Regards