doesn’t work

Hi
I have downloaded this plugin a few months back. the client put website on hold and now we are trying it again but it doesn’t work.
I have authorisation ok. Everything is saving. but when i press “import” or “start” button nothing happens. I had 2 hrs to do transfer and it is not working.
when I do one time import from izettle nothing happens. no changes, no products uploaded nothing showing in izettle wp tab.

Please advise on how to proceed. My client is ready to pay for monthly subscription as soon as test works.
I can also give you user access if you wish.
This is a bit urgent so a quick feedback would be welcome
Thank you for your help