Hi,
It looks like as if a file corruption issue, and the plugin data is printed into the header.
The best possible solution to this is to try to completely remove the plugin and reinstall it again, to make sure all the files and the database are completely in tact:
1. Make sure to delete the plugin completely – this is very important.
2. Then, download the latest version via codecanyon dashboard and install it via the plugin manager.
3. Try activating the plugin, even if some errors pop-up, navigate to the maintenance page and do a full plugin wipe: https://documentation.ajaxsearchpro.com/installation-instructions/uninstallation-and-reset#complete-uninstallation-including-all-plugin-data-wipe
4. Delete the plugin again via the plugin manager.
5. Install and activate again – now no error messages should show up whatsoever.
This should completely clear all possible integrity issues.