Necro means start a discussion in an old post. The problem is, that game was long time in development, so answering or ask the same question in a 2 year old topic doesn't make any sense since it is not really the same game as 2 years before (lot of changes). Best thing is just to open a new topic with your question.
About your problem, how do you tried to download the save? Have you used the build-in function (start new game/continue - > export & and cloud save - > import from cloud)?
If that does not work, you could try it manually vie Google takeout (export Google play games)
go to https://takeout.google.com/settings/takeout
with your google account. then choose Google Play Games for export.
After Downloading the archive and unzip that, there is a Exiled Kingdoms Folder.
Inside that, there is a file called Data.bin thats the export file, just put it on your phone (send yourself an email) and rename it to EK.bak. then you can import that file (... - > import from file)