I moved from Hotmail to gmail over a year ago and was using it no problem, my own opinion is that when I bought a new samsung smartphone 3 weeks ago, the Samsung shop changed my data from my Redmi and I was asked to use a new password for google and I gave her one, I used it fine till about a week ago and tried to sign in to my gmail account and that's when things started to go haywire.
I have a note of about 6 passwords I have given Google and every time I tried to use one it was not accepted.
The local computer shop guy tried to get me a google password and he had the same problem as me.