front builder just keep loading

Sorry my english, ... I´m using front builder to edit the panino Theme for a customer site. but, i take a break then wen i come back try to acces to edit more the theme but never enter again on the front builder. Is the second time. the first i uninstall the theme because cleaning the cache is not enougth. but now is happen again when i was in the 80% of the work. and i don´t know what to do