HDFC Bank — not receiving otp

Hi, i have updated my uk number in my bank account a few months ago, and i have been getting all the opts instantly on that number, but i am not getting them anymore. It works sometimes and sometimes it doesn't.
I didn't get an otp a day before then it worked yesterday, and now it stopped working again. I am trying to do a payment online and i am not able to receive an otp now. This is very annoying and frustrating.
Can you please check why this is happening?
Let me know if you need any details?