WhatsApp Verification Code Not Received on Xiaomi Redmi 9

I have been unable to verify my WhatsApp number on my Xiaomi Redmi 9 for a long time, despite trying many times. I am registering a number with the country code +256. Each time I start the verification process, the SMS code never arrives, and after some time, WhatsApp tells me to download the official WhatsApp application, even though I am already using the official app. To solve this, I have already tried common steps such as repeating the verification process many times and reinstalling and restarting, but the problem still continues, and I cannot activate my number on WhatsApp. I expect WhatsApp to review this situation, explain clearly why my number cannot be verified, and provide me with a clear, applicable solution so that I can successfully activate my WhatsApp account with my current number.