Pro Sites Plugin Issue during install???

Trying to activate the Pro Sites plugin and get this message?

Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM in /home/content/18/7659718/html/lucidhive/wp-content/plugins/pro-sites/pro-sites-files/lib/ProSites/Module/Taxamo/lib/Taxamo/Swagger.php on line 185