It is because if the total response count of the survey crosses 50 then the bulk edit option is disabled by default for the survey (this response count includes the completed, started, and terminated responses). It is the count that reflects on the survey dashboard (screenshot: https://prnt.sc/7002DThcT7v-).

However, if you need to enable the bulk edit button for any question, then you will need to delete the responses from the survey and reduce the total response count below 50, in that case, the Bulk edit option will be enabled again. Please download the raw data before making any changes to the survey, as the responses once deleted cannot be retrieved. Help file on deleting the responses: https://www.questionpro.com/help/response-viewer.html

Please note we strongly suggest not to delete/adjust answer options (on a live survey), please do so only if it is absolutely necessary and at your own risk. To know more about the implications and issues of deleting/editing answer options, please check: https://www.questionpro.com/help/editing-live-survey.html