Google error: Network unreachable

[Emplehod]

I have three sites all running on my own server.  Two passed fine, but one has gotten this error about 4 times:

Network unreachable: Network unreachable
We encountered an error while trying to access your Sitemap. Please ensure your Sitemap follows our guidelines and can be accessed at the location you provided and then resubmit.

The sitemap can be reached fine.  I don't understand.  This is the URL:

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[ADDED}

I just thought of something that may be relevant.  I am using a service to block IPs from certain countries.  I guess Google isn't doing this from the United States.  I have removed the blocking and getting tested again.

[XML-Sitemaps Support]

Hello,

yes, probably your configuration has blocked google bots.

[Emplehod]

I completely unblocked my sites the date of my first post and I'm still getting this error every time Google crawls my sites:

Network unreachable: Network unreachable
We encountered an error while trying to access your Sitemap. Please ensure your Sitemap follows our guidelines and can be accessed at the location you provided and then resubmit.

Is there some different format Google looks for?  I'm using the sitemap.xml file.

[XML-Sitemaps Support]

"Network unreachable" error means that they were not even able to connect to it, so that's not a format related problem.