Can't receive mobile phone SMS message for the Gaijin Pass Two-Step authentication app

[ComradeChuanJianguo 0]

Hello, I was trying to make some changes to my Gaijin Pass Two-step authentication app on my phone recently, Before any changes, I need to get a mobile phone verification code (SMS message) as a security verification. But after trying several times I still can't receive any SMS message through imessage from Gaijin pass. At first, I thought it was some problem related to my phone or data operator. Then I tried to receive SMS messages from other apps (TikTok, Amazon) but they all worked and I am hundred percent sure the phone number I linked on the Two-step authentication app is functioning. So I really have no idea what the problem is. Can somebody tell me how to fix it? Thanks!