Bro i faced the same issue but the solution i find while logging from my iPhone try to log in from google chrome if it doesn’t work first time try log in second time from safari u can log in.I am Pakistani citizen and had applied for Canada visa from online service through Houston , USA. After 29th of April I cant access my online account. After putting valid username and password it is taking me back on main page. I tried different systems and browser (with latest version) still failed.
And wise versa means log in first from safari if it shows same error go to google chrome and log in from there it will work.