MailPoet “404” error page after entering email for newsletter

Hi MailPoet,
Yesterday I had problems that when subscribing for the newletter that there was an error message and a subscription wasn’t possible…this has now gone, but has been replaced by another error message.
1. I can now enter an email address and click the registration link, however then the website goes to an error 404 “this page cannot be found” page.

2. People who subscribe appear in the backend in the list, but do not receive an email to confirm their subscription. If I manually send an email this is also not received.

I send via the mailpoet sending service. The set up is always to go to a mailpoet page after confirmation, unsubscribe etc. MailPoet latest version, just updated this morning.

The website is https://www.alexclarkart.de, the newsletter registration page is https://alexclarkart.de/newsletter/

I hope you can help.

Thanks

Andy`

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