S21 Notice a day out

Possession - Section 8 and Section 21

Hi, I tried to bring possession proceedings under the accelerated scheme, but the district judge said the date on the s21 notice was a day out and set it for a hearing. It is to be heard next week and I will be going to court. There has been no defence filed and the tenant is not likely to attend (she needs the order to be rehoused).
Do you have any helpful tips or case law that I could use to assist in getting the order?
The alternative is to start again which is costly for me and ultimately for the tenant.
And help very gratefully received. Thanks