Mailchimp module show an error "Invalid api key" impossible to go on with the wizard and connect them

[PacificiCorrado]

Hi,

we have this problem "invalid api key": 

we have followed the steps indicated here https://mailchimp.com/help/connect-or-disconnect-mailchimp-for-prestashop/#Connect_your_store several times, without ever being successful. Obviously it worked before, the shop had been connected with Mailchimp for many years.

The Mailchimp module does not use the KEY API, but as the support wrote us it uses OATH:

"The Mailchimp for Prestashop does not use API keys to connect to your account, it uses OATH. So the fact that the error says "Invalid API Key" is odd."

For a few weeks we have been having problems with the connection between PrestaShop and Mailchimp, the developers of the module do not respond, and when they do it those very rare occasions, they tell us to contact Mailchimp directly. The support, however, is courteous but also not very productive. when we contact Mailchimp support i have to repeat the problem every time, it is really frustrating.
As Trustpilot https://www.trustpilot.com/review/www.mailchimp.com has amply demonstrated, Mailchimp has a very bad reputation for which we are considering using another service.
If anyone has had a similar problem in the meantime and solved it please let us know how.
Thanks for any replies.

PC