Help fix ‘500 Internal server error’

详细信息

I am working on a Wordpress website hosted by Blacknight. I uploaded a plugin to speed up the site called Seraphinite Accelerator. When I activated it, the whole site crashed and the display said - ‘Error occurred - 500 internal server error’
I cannot access the wp dashboard to remove the plugin. I followed direction to go to the File manager on Blacknight and rename the plugin which should deactivate all plugins. This didn’t work. I need help to fix this please.