UpdateListItems -List no longer exists SOAP 0x81020026

We have a an old SharePoint integration to our system, and we want to migrate the SharePoint 2013 into SharePoint online, but after we migrate the data the UpdateListItems calls won't work anymore... even the read calls woks fine and the user can manipulate data through SharePoint website.

(I created a new list, with the same user, add a row, and try to modify it via SoapUI, same result...)

<ErrorCode>0x81020026</ErrorCode>
<ErrorText>The list that is referenced here no longer exists.</ErrorText>

<z:row ows_ID="1" ...

Any suggestion/guess would be helpful.