Mail section of contact form suddenly empty – mails not sending

I run a WordPress Multisite which has basically three versions of the same blog in three languages.

I created contact form on the Dutch version of the site, which I tested and was working properly.

I duplicated the Dutch site to create the English version of it with a site duplicator plugin for multisites.

I then also duplicated the Dutch contact form to create an English version of it. As the duplicated version was also in Dutch and I couldn’t seem to change the language settings for an existing form, I created a new form and copied the form information of the Dutch one to the English one.

I tried to send a message through the Dutch contact form this morning and got this message (in Dutch): Failed to send your message. Please try later or contact the administrator by another method.

I checked the contact form settings and the entire “Mail” section was empty. Now I don’t know when this happened, but I suspect it probably happened during the duplication of my website or during the duplication of the contact form. I suspect it has to do with the way in which Contact Form works with Multisite, also cause in the admin section of the Dutch version I am able to see only the Dutch contact form, whereas in the English version I see both the English and Dutch versions.

Any help is appreciated.

https://www.ads-software.com/plugins/contact-form-7/