check if you can post comments on the problematic planner tasks via planner portal (https://tasks.office.com) ?. If you can able to post comments from the Planner web portal successfully and face issues only with our tool, then please send us the log file by following the steps shown in the below image. Also, please send us the problematic Trello JSON file for further analysis.

Note: If the comments exist in your Trello JSON file, then the tool will simply import it. And we are importing the comments that are typed by the user alone, and we don’t import user activities (Actions) in the card (example actions: File attached, user-added. etc..) due to technical limitation. So please confirm that the not imported comments are actions or actual comments.