This is a generic error message that QuickBooks provides and could indicate several different problems.
Exporting Invoices: An XML generation error is commonly caused by invoices with no line items or cost. To rectify this error, simply go to the invoices section of LMN time and un-queue the invoices with a $0 total.
Exporting Estimates: An XML generation error can be caused by an invalid email address in LMN, extensive notes in work/ service area(s) or $0 value in work/ service area(s).
Invalid email address: Open CRM, select customer, contacts, ensure a valid email address is listed.
Extensive notes: Open Estimate, click work/ service area(s) and reduce or remove extensive notes.
$0 workarea/ service(s): Enter value or remove $0 work/service area(s).
Exporting Timesheets: An XML generation error can be a result of an emoji added to timesheet notes. To resolve, open timesheet and remove the emoji.