Hi Vicky,
Thanks for coming back. You may need to join the Google Group for you to use the reply to author option. Nonetheless, I checked your script and it seems that the issue is with the
Link Checker script not being fully compatible with the new
Google Ads Scripts Beta. For available solution scripts in beta, please see this
link and I regret to inform you that the beta version of the link checker script is not available currently. If you are keen on migrating the script to beta, you can refer to the following links that may be of help to you.
On the other hand, disabling the new scripts experience option should address the issue on your end, if you will not be able to migrate the script right away.
Let me know if you need anything else.