if its still not updating, add print(formset.errors) and see what wrong from you console
{'join': ['This field is required.'], 'regno': ['This field is required.'], 'sub2': ['This field is required.'], 'subcode5': ['This field is required.'], 'branch': ['This field is required.'], 'section': ['This field is required.'], 'subl1': ['This field is required.'], 'subl2': ['This field is required.'], 'subcodel1': ['This field is required.'], 'sub4': ['This field is required.'], 'id': ['This field is required.'], 'cursem': ['This field is required.'], 'subcode1': ['This field is required.'], 'sub1': ['This field is required.'], 'subcode2': ['This field is required.'], 'subcode3': ['This field is required.'], 'subcodel3': ['This field is required.'], 'subcodel2': ['This field is required.'], 'sub5': ['This field is required.'], 'subcode4': ['This field is required.'], 'sub6': ['This field is required.'], 'subcode6': ['This field is required.'], 'subcodel4': ['This field is required.'], 'sub3': ['This field is required.'], 'type': ['This field is required.']}]