I know the feeling when nothing works after trying everything. Despite this, I appreciate your efforts to try to troubleshoot this, and I'll shed some light on the process to help you.
We're unable to export data from QB Mac to a QBO company that has an existing payroll subscription. In the article about conversion, this is one of the points that need to be considered before going into the process. This is also stated in the articles about fixing errors when converting data.
What I can suggest is to create a new QBO company (without payroll) and export your QB Mac data to it. You can use the same credentials when adding another QBO company to your Intuit account.