You may have entered the wrong telephone number in the app. You can check this as follows:
On the page where you receive the SMS code, click
‘send code via email instead’.
You will get a link in the email. If you go to email in the telephone and click on the link it will take you directly to the app.
Once you’re in the app, go to the hamburger button (three bars) at the top left and select ‘account’.
Check that you have entered the correct telephone number. If the telephone number is wrong, correct it; the SMS code will thenceforth function. Because the SMS code is a one-time code, you will get a new one every time you need to log in.