Contact Form 7: No messaging via smartphone

More or less all of a sudden, I can no longer make enquiries with my smartphone on my websites where I use Contact Form 7. On the PC, everything works perfectly. But not on the smartphone. I don’t even get an error message, it just takes a long time to load and nothing happens. I have already installed Easy WP SMTP. Apparently that’s not the problem. I recently switched to PHP 8.0. But that shouldn’t be a problem either. Is there perhaps a solution here? Otherwise I have to change to another plugin. I would like to save myself the effort.
Many thanks for suggestions 🙂

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