The formal representation was submitted on 14 December and it was via e-mail.
I have attached the e-mail which contained the NoR . The e-mail was sent on 13 January.
Then the date of service of the Notice of Rejection is 13 January, so you have until 9 February 2025 to appeal. I wouldn't wait, you might as well appeal now, the system will assume the appeal is out of time and ask you why, but all you need to do is explain that you did not receive the Notice of Rejection in the post and only got a copy via email after you chased it up, attach a copy of the NoR and crucially attach a copy of the covering email.
Alternatively you can instruct me to represent you, I'll send you a PM in case you'd prefer that.