I cannot get the cellular data account on my ipad. I have gotten it in the past

I Have an ipad . I'm trying to get my cellular data turned on and all I get is an error 500-- internal server error; the server encountered an unexpected condition which prevented it from fulfilling the request. I have no internet service, but I do have wiFi. I have powered down.

WHen I go to settings>cellular data> view my account I get the error code