Thunderbird doesn't work as default email client when sharing pdf attachments. Works fine if Mail is the default client

With Tbird set as the default email client, whenever I try to email the pdf, a message pops up that the default client can't handle sending the attachment. It works all the time if the native Mac Mail software is the default client.. This forces me to save the pdf file, go to Tbird to send a message and then have to find the file in the folder structure to add as an attachment.