Setting up VK and FB?

Question

Facebook

Good day to all, VK and FB have a function to receive messages from users.
I tried to implement this feature and tested it: as a result, nothing comes from VK, one incomplete message without files came from FB, subsequent messages also refused to come. Explain to the PJ, I'm doing something wrong or misunderstood the capabilities of this function, and in fact, messages and files cannot be sent to the mail through this function. If the latter, then maybe someone knows other options to implement the possibility that all messages and files sent by users on VK and FB come to my mail?
I planned that all messages and files sent by users to my VK and FB would come to one of my mail. The question is how to implement it?
Thank you in advance for your help!