After upgrading from TYPO3 12 to 13, DOI is no longer possible

[format-gmbh]

I have integrated the "linawolf/form_double_opt_in" set.
I have checked the form with the finisher for DOI.

After submitting the form, the message is immediately sent to the recipient of the form. No DOI email is sent.

TYPO3 13.4.22
EXT:form_double_opt_in 13.2.3
PHP 8.3.27
composer mode