平时只看首页。你应该可以通过把密码改回去试试。手机的gmail不会自动sign out的。 gmail一般会不让重复最近的几个密码。刚搜了下，是最近100个。另外就是如果找不到，也许就是不支持。你可以按你手机的型号，看看能不能root，或者刷bootloader。如果是几年前常见的型号，应该是有希望的。

https://www.quora.com/Gmail-is-not-allowing-me-to-use-the-old-password-What-should-I-do
There is a solution. Google save only last 100 password entry in their database and if you want to set password that falls into last 100 saved password then Google will not allow you to set it up.

So if you can spend 10 min time, changing password for 100 times with some dummy one, you can able to set the same password you wish to have.

I will give you an example to make it clear:

If you want to set "quora123" as a gmail password but you used it earlier, google will not allow you to do so. For that you need to replace last 100 password entry with some dummy one-

abcd1
abcd2
abcd3
abcd4
abcd5