If you have not been paid, then you're doing it wrong.
Clients are not obligated to respond.
If I a have an hourly contract, I get paid AUTOMATICALLY if clients do not respond.
If I have a fixed-price contract, I click the "Submit Work / Request Payment" button, and then I get paid AUTOMATICALLY if clients do not respond.
If you HAVE been paid, and you are simply worried about the client's health or something, then don't worry about this. Not your concern.
If you have concerns about the website, then don't worry about it. This is the client's project, not your project.
If you have followed the client's instructions and done the work that the client asked you to do, then that's all you can do. If the client wants to communicate further with you, then he will do so.
Think of it like this:
4 months ago, you went to a restaurant and ate breakfast. You paid for the food, and left.
You have not gone back. Did the waiter come look for you and ask what you want to eat next? No. If you want to eat there, you'll go back there. You know where the restaurant is.
