I keep being denied access to my main email account, WHY?

[Juggery65]

Can someone please explain explain to me why I keep randomly being denied access to my main email account?

I have my main account open, and then I switch from it to my secondary account to check my mail there, which I can access as usual, but then when I try to switch back to my main account moments later I am denied access to it with 'password is incorrect'. The password is NOT incorrect, because I have just used it to access the same account minutes/hours before, before I switched to the secondary one.

OK then, I think, I'll log in to My Account to see if I can change the password from there and regain entry, but for some reason it isn't allowing me to do that.

This keeps randomly happening since the last 'fantastic' email service upgrade, I get locked out for no apparent reason for a while (anything up to a day or so) and then one time I'll just type in the so-called 'incorrect' password, exactly as before when it's been rejected, and as if by magic I'm suddenly granted access to my own emails again.

This is only affecting the one account, but it is my primary account where I do all my important daily stuff. This has happened at least three times now in the last couple of months and it just isn't good enough. What is going on?

[Gondola]

You don't need to change the mailbox password.

Usually when this happens it's because your browser has auto-filled in the wrong password. So, you see when you try to login to the second account that the browser has auto-filled in the previous account email address and password.

You then change the login email address but the password for the previous login remains and you get the incorrect password error.

So you have to enter both the email address and password to override what the browser is doing in its quest to be helpful.