All employers with 20 or more employees have had to report via single touch pay roll since 1 April 2018 so must now no longer use manager.io for payroll
Only employers with 19 of fewer employees have until 1 July 2019 to comply with STP reporting requirements but are encouraged to achieve it prior to that time. After then ALL employers will no longer be able to use manager.io for payroll on Australia.
It is a difficult judgement call to guess if Manager.io will be compliant with STP by 1 July 2019 or not. I believe it requires API support and an external supplier to offer a compliant product. I suspect at this time it is probably wise for all employers to look at moving their payroll to another platform given this uncertainty.