I notice you are using a MAC

Your image shows the right click on attachment drop down menu shows 'Remove Attachment' is disabled.

Are you able to right click in the attachment area - but to the right of the attachment and select 'Remove all attachments' ?

What version of Thunderbird are you using ? What language are you using?

thank you for your reply

even if right click delete is displayed in gray i can not click

version 146.0.1 Japanese

sorry I'm not good at English

it was solved when I reinstalled it

I'm sorry for the for the trouble thank you very much