Jetpack connection identity crisis site can't communicate with jetpack

When I go to site stats, I get this message:

unknown_token: It looks like your Jetpack connection is broken. Try disconnecting from WordPress.com then reconnecting.

So, I tried disconnecting through wordpress.com but I can’t reconnect because when I click “Link your account to wordpress.com” through my site’s admin area, I get this error:

Invalid request, please go back and try again.
Error Code: invalid_client
Error Message: Unknown client_id.

My debug panel shows the the following 2 errors:

1.
Something has gotten mixed up in your jetpack connection!

2.
Your site cannot communicate with Jetpack properly.

SELF:
	Array
(
    [headers] => Array
        (
            [server] => nginx
            [date] => Fri, 31 Jul 2015 13:47:04 GMT
            [content-type] => text/plain;charset=utf-8
            [connection] => close
            [x-pingback] => https://jetpack.wordpress.com/xmlrpc.php
            [expires] => Wed, 11 Jan 1984 05:00:00 GMT
            [cache-control] => no-cache, must-revalidate, max-age=60
            [pragma] => no-cache
            [x-hacker] => Jetpack Test
            [x-ac] => 3.dfw _dfw
        )

    [body] => {"error":"Jetpack not connected","error_description":"We were unable to find a Jetpack instance on your site. Please connect Jetpack to your WordPress.com account from within your WordPress admin."}
    [response] => Array
        (
            [code] => 400
            [message] => Bad Request
        )

    [cookies] => Array
        (
        )

    [filename] =>
)

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