I can't send emails in bulk

Your software
My Mautic version is: v3.3.3
My PHP version is: 7.4.27
My Database type and version is:

Your problem
My problem is: yesterday I wanted to send an email to a contact segment, like I do every month. But it didn’t worked. The sending process stayed blocked and I’m not able neither to send nor to edit the email.

What can I do?