impossible activate revolution slider plugin in RookTheme

Hi everybody! please help me… I bought ROOK theme last week and I’m trying to start… but the Revolution Slider plugin (with is included) doesn’t work. I could install it BUT I can’t activate it.

this is the message:

Fatal error : Uncaught Error: operator not supported for strings in /web/htdocs/ Stack trace: #0/web/htdocs/ UniteBaseAdminClassRev::addMetaBox(‘Revolution Slid…’, Object(UniteSettingsAdvancedRev), Array, NULL) #1 /web/htdocs/ RevSliderAdmin->addSliderMetaBox() #2/web/htdocs/ RevSliderAdmin->init() #3 /web/htdocs/ RevSliderAdmin->__construct(’/web/htdocs/www…’) #4/web/htdocs/ include(’/web/htdocs/www…’) #5 /web/htdocs/ plugin_sandbox_scrape(‘revslider/revsl…’) #6 {main} thrown in /web/htdocs/ on line 73

my php version is update to the latest PHP 7.3, if this had been the problem…
thank for your help!

I can see theme has last updated:
Last Update 28 November 16

make sure you are using latest version slider plugin, plugin has come with theme bundle. very outdated theme may be php version compatibility issues. please contact theme author and ask them support here: