假如密钥如下：
ABCDEFGABCEDFG[...省略...]ABCDEFGA====输入密钥时可能提示“密钥无效”，此时将字符串最后的所有等号（即“=”）都去掉，再输入试试：
ABCDEFGABCEDFG[...省略...]ABCDEFGA来源：
《Google Authenticator on Apple devices, certain secrets are not valid》，ajaali answered Jul 24, 2015 at 15:56：https://stackoverflow.com/questions/29173288/google-authenticator-on-apple-devices-certain-secrets-are-not-valid
It turns out that Google Authenticator doesn’t like = signs in the IPhone App, but doesn’t complain in Android.
The pad character (=) does not have a binary representation in BASE32; it is inserted into the BASE32 text as a placeholder to maintain 40-bit alignment
《Google Authenticator(谷歌身份验证器)在苹果手机上IOS系统中 输入密钥时提示密钥无效的解决方案》，2019-11-07，Bingo_BIG：https://blog.csdn.net/lybwwp/article/details/102949344