The Host has to implement a minimum required interfaces like IMessage :
Host Requirements for VST 3 Support - VST 3 Developer Portal (steinbergmedia.github.io)
The host could implement the new interface (since VST 3.7.9) IDataExchangeHandler [3.7.9] Data Transfert Between Processor/Controller - VST 3 Developer Portal (steinbergmedia.github.io).
Try to check your host with the hostchecker plug-in: VST 3 Plug-in Examples - VST 3 Developer Portal (steinbergmedia.github.io)