Subscribe with email adress not working (error)

We have a problem with the mailpoet subscribe.
When a customer enter his email adress and click on ‘subscribe’ there is a error in red on the screen.
Here is a screenshot (it’s Dutch)
An error occurred while executing a request, please try again later.

https://i.ibb.co/fdJ97rJ/Mailpoet-abboneer.jpg

We can not find any errors on our site.
We use the Astra theme.
Also the plugin is updated.
Hope someone can help us ??