Pro Sites show error on activation

Again error on activation. I wonder if there is any problem with my instalation, which is fresh new and just have WPMUDEV plugins installed. First humingbird and now Pro Sites.
Check the alert message:
Plugin could not be activated because it triggered a fatal error.
Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM in /home/boxla647/public_html/wp-content/plugins/pro-sites/pro-sites-files/lib/ProSites/Module/Taxamo/lib/Taxamo/Swagger.php on line 185
Thanks for anyone looking at that!