Not getting verification codes via SMS

I'm having the exact same issues as kaniOu who Posted on Mar 21, 2021 4:09 PM

I am currently using iphone XR. However, I am NOT able to receive texts for verifications/security codes from short SMS numbers. I have not received any text messages that were sent with the verification code and I previously did receive them from the exact same websites. This is getting to be a real problem as I cannot get into my accounts. Thanks for helping with this issue.