Rev slider – stopping access to WP admin

Hi There – I have two licences for fortuna – with both I am having issues. On my existing webpage I cannot access wp-admin (detail of error message below). I have also tried installing a second copy of the theme for a new website I am building using a standard WP install on 1&1. I get multiple issues regarding access to lisences with the builder etc.

Any help welcome please.

Fatal error: Uncaught Error: [] operator not supported for strings in /homepages/1/d643780480/htdocs/oxxx/wordpress/wp-content/plugins/revslider/includes/framework/base-admin.class.php:69 Stack trace: #0 /homepages/1/d643780480/htdocs/oxxx/wordpress/wp-content/plugins/revslider/admin/revslider-admin.class.php(407): RevSliderBaseAdmin::addMetaBox(‘Revolution Slid…’, ”, Array, NULL) #1 /homepages/1/d643780480/htdocs/oxxx/wordpress/wp-content/plugins/revslider/admin/revslider-admin.class.php(66): RevSliderAdmin->addSliderMetaBox() #2 /homepages/1/d643780480/htdocs/oxxx/wordpress/wp-content/plugins/revslider/admin/revslider-admin.class.php(43): RevSliderAdmin->init() #3 /homepages/1/d643780480/htdocs/oxxx/wordpress/wp-content/plugins/revslider/revslider.php(150): RevSliderAdmin->__construct(‘/homepages/1/d6…’) #4 /homepages/1/d643780480/htdocs/oxxx/wordpress/wp-settings.php(215): include_once(‘/homepages/1/d6…’) #5 /homepages/1/d643780480/htdocs/oxxx/wordpress/wp-config. in /homepages/1/d643780480/htdocs/xxxg/wordpress/wp-content/plugins/revslider/includes/framework/base-admin.class.php on line 69