i have found the issue is not the null, it was a char before null that caused the error
Loader::loadHelpers($this, ['Date' => [ null, 'UTC', Configure::get('Blesta.company_timezone')]]);
Loader::loadHelpers($this, ['Date' => [null, 'UTC', Configure::get('Blesta.company_timezone')]]);
Invoice creation automation task runs once per day. If it already ran today, then invoices won't be generated again until tomorrow. So if you're billing 14 days in advance, and it's 8 days until the service is set to renew, then it should be invoiced at the next run.