i had this problem with a site.
do you have the redis object cache plugin installed and active? if so, remove it..
(i've only used this redis plugin, other object cache plugins may cause the same problems)
and also remove any wp-cli specific info from wp-config.php
(typically an if statement setting db_host to 127.0.0.1:3306 if wp-cli is being used, just remove that whole lot and just have 'define ('DB_HOST', "localhost"); )
also, check for any php errors on the site, you may need to enable debug mode to see some of them..
any of these can stop wp-cli connecting to the site properly, which will cause the problem you're having.
https://community.enhance.com/d/3455-wordpress-manager-sso