Apple cannot receive SMS verification code. What happened?

The reasons why Apple can't receive SMS verification code and the solutions are as follows:

Cell phone signal problem: If the cell phone signal in the area is poor, you will not be able to receive short messages normally. You can try to move your position or go to an open place to bring a signal of improvement.

Network Settings: Check whether airplane mode is turned on or short message function is turned off in the network settings. Please make sure that the network connection is normal and the SMS function is turned on.

Block spam message filter: Apple's mobile phone has a built-in "spam message filter", which will automatically block some messages that are considered spam messages. Please check whether the SMS with important verification code is misjudged as spam and make corresponding adjustments.