Dear Yui,
Thanx for answering / replying to my posted topic.
If I understand this well, than I’m not so smart to buy the Pro-version to solve the not working calculation. But better first solve it in the free version.
In case I buy a Pro-version I have no rights confirming the WordPress policy.
I have to lean on de PRO-version support of the developer. But I agree and for me it’s clearly that any support should be prohibited to ask for any credentials. I’m fortunate aware of the danger to give any login information.
I’ll contact the developer again and ask for a decently, secure solution. If not, than deactivate, delete the plugin and search for an alternative.
Thanx again.