[2020] Keep getting error code trying to regain account?

Have played this game near-constantly since 2015, on Android, and just today got an iPhone. I tried linking new device to facebook to pull up my linked account, which i had read was the way to go about it, but I keep getting Error Code 9.0 and am unable to grab it. I would be absolutely devastated to lose everything but am frustrated trying to get it to work to no avail.