Log in button disabled

Recently, the log in button on my WordPress install has become disabled. I recently udpated a few plug-ins (BuddyPress and WP-SpamShield), and I noticed the issue after. I have reverted both to the earlier versions, but the issue remains.

Here’s the HTML that is being output for the button to submit the form.

<input type="submit" name="wp-submit" id="wp-submit" class="button button-primary button-large" value="Log In" disabled="">

It’s odd, but I have a staging site with the same plugins and configuration and the button is not disabled. The HTML does not have the “disabled” included in this line.

I have tried disabling each of my plugins one by one, but that doesn’t fix the issue.

Any idea where that “disabled” is being generated and what I can do to fix this so users can log in again?

The page I need help with: [log in to see the link]