Please note that you wrote to the ResearchGate community, not to the RG team. However, it is not worth writing to them. ResearchGate is neither a journal nor a publisher, you cannot "publish" a paper here. It is a platform for papers published in journals, or to present unpublished texts, data etc. Therefore you will not get a "Notification of Acceptance". See also "Is ResearchGate a publisher?" in https://help.researchgate.net/hc/en-us/articles/14292596164753.