One of the referees is unresponsive - Extended deadline is nearing

[throwawayaccount40]

Hello.

I have applied for the master's program. I submitted my application, and one of the two referees submitted his LOR the day they received the link. The other referee is not responding at all. He agreed to write a LOR for me and provided his contact information. I sent a follow-up email when I submitted my application to remind them. The deadline approached, and when I saw they had not opened the link (which I can check from my applicant portal), I emailed the programme coordinator, who replied back saying they would consider the letters of recommendation until mid-February. So, I emailed my referee again to send a reminder about the extended deadline, but I still got no response. I have been waiting, checking my email every hour.

The reason I was rooting for this specific referee is that I have done some written research work under him, and I thought it would be great if he could attest to my skills and interests in this area.

I do not know what went wrong. Because, when I asked him if he would write a LOR for me and, following that, when I asked for his details to add him as a referee, he was very responsive and quick to reply. Now suddenly, he is not.

I am really interested in this program. And, I put a lot of effort in the application essay as well, coupled with the application fee. This university is my top choice. In such cases, do universities still consider the application if one of the referees never gives the LOR? What more can I do? Some insights and guidance would be really helpful.