if you are using Digi, you can try this method, this is due to Digi sim not able to receive some of the international sms, especially new sim from this few years back.
I believe Digi blocked some of the "spam" sms on recent year, maybe due to too many complaint about the extra charges.
I got this problem when the xiaomi phone always show Sim activation notification on new phone, and also facing issue not able to register telegram due to sms activation code not receive. By follow the below steps, all my problem solved.
prepaid
1. dial *128#
2. My Account
3. Account info
4. Account settings
5. Voicemail
6. Other setup
select 3. Outdial Message On.
postpaid
1. dial *128#
2. More
3. Digi Rewards & Services
4. Voicemail
5. Other setup
select 3. Outdial Message On.
You can turn it off once the activation done.
Please note there might some RM0.xx sms charges apply.
No wonder, I can't even received whatsapp verify sms.