WP itself will not update to 5.5.3 after updatin the X theme. My API is installed on the site in question

Congratulations, you’ve successfully updated X! Be sure to check out the release notes and changelog to see all that has changed, especially if you’re utilizing any additional plugins or have made modifications to your website via a child theme.

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Downloading update from https://downloads.wordpress.org/release/wordpress-5.5.3-no-content.zip…

The authenticity of wordpress-5.5.3-no-content.zip could not be verified as no signature was found.

Unpacking the update…

Could not copy file.: wordpress/wp-includes/css/media-views-rtl.css

Installation Failed

Hello @enigmamac,

Thanks for writing to us.

It seems that you have updated your theme but your WordPress core is not updated properly. To upgrade WordPress manually please check these articles.

Hope it helps

I have tried to update manually with no success several times. I keep getting the message that I originally posted.

Please tell me how to FIX this problem. Please respond to this specific error message, not some standard answer like you posted earlier:

I have paid support on the “X” theme. How do I contact support?

Hello @enigmamac,

We believe that this issue has something to do with your WP core files update and not with the theme. We would highly suggest checking with your host/server admin on the issue you are experiencing.

Or maybe you can update your WordPress core files manually:

Please understand that this error is between WordPress and your hosting server. There might be some misconfiguration on the server that is resulting to this issue. It could turned out that the server was too full. You may delete some of the old backups to make room, and then the upgrade WordPress core files again.

Thank you for your understanding.