Couldn't find meta-data for provider with authority com.example.postouapp.com.postouapp.provider, com.whatsapp, null)

[vkbaloda]

This error comes when uses the normal shareToWhatsapp method with imageFile URL and some message.

This must be happening because you used your own apps applicationId when getting file path with FileProvider. I think it should be something like this (use the clients applicationId):
FileProvider.getUriForFile(context, context.getApplicationContext().getPackageName() + ".provider", file);