"Connection lost : your session has expired"

Sooooo.

Since I started the game last week, I cannot log into the game with my google play games account.

The only error message I have is this : "Connection lost : your session has expired. Either another device has logged into this account, or it has been 24 hours since you last logged in."

If I click on "reload", I have the start menu, then the google play games loggin green splashscreen, then the "choose account for Google Play Games". 

I choose my account, and then I have the following menu : 

"Sign in to google play?
Advantages of Google Play : 

- Use the same account across multiple Android devices

- Restore your account in the event of loss of your device

- Gain access to Google Play Achievements"

I have two buttons: "Play as Guest" and "Sign into Google Play".

- If I play as guest everything works fine but half of the google play function works. (in game, I have the "log into google play" button instead of "log off google play", my achievements are not visible, but google play game still know I played the game.
That is how I play for now. I don't like it because I don't want to loose my save files and will soon change my phone.

- If I click on "Sign into Google Play", I have again the google play games splash screen, "log in", my welcome message from google play game with my name on it, and then the very same error message I copied earlier : "connection lost, your session has expired" and so forth.


I tried everything : 

- Maybe my tablet would conflict with my phone (same account, but I don't have the game on it) so I powered my tablet off.
- Maybe my computer would conflict with my phone (in my google account settings, it says my PC is a google device since I hage google Drive on it) so I powered off my computer also.
Didn't work, kept those powered off for 5 hours, tried again, didn't work.
- Changed all my confidentiality of google play games, permitted access to google plus to apps with less security, allowed almost everything on my accounts, nothing.
- deactivated my wi-fi on my phone to try to log in with 3G/4G : nope.

And a lot of other things I can't even remember.


So. The thing is : No google play achievements : not a problem. I can live without it.

But I would love to have a way to play on multiple devices (including my tablet) and to be able to sell the phone I use now when the time will come without saying to myself that I have to loose ALL my savegame.

Oh, and I did an other try to confirm this sentense : donwloaded SWGOH on my tablet, started a new game, tried to log in google play game...

Same bug. (I tend to think it has to do with google play account but what ???)

THanks for you help.