Hi,
I have a similar problem. I installed the Updraft Plus plugin for the add on – for Migrator. Successfully installed the plugin however cannot connect to Updraft Plus server. Keep getting a 406 error message – Not Acceptable.
On talking to the webhosting provider tech support – they seem to have some type of security rules in place which is not an issue for the current site I was able to connect Updraft Plus Migrator to.
Any thoughts how to overcome this – seems different webhosting providers have different security rules in place for the plugin.