I reinstalled my vps masternode and now I get this error "the public URI provided is already registered" . how to resolve?
You would have needed to back up the hmac keys if you did a reinstall. I don't believe you can register a new node under an IP address that another node is registered under.
You can set up a fresh vps, but you will lose your position in the rewards queue unless you import the hmac keys from your previously registered node.