这个问题通常是由于提供的Twilio账户凭据不正确造成的。请确保在Twilio提供的控制面板中使用正确的AccountSid和AuthToken。下面是正确设置Twilio客户端的代码示例：

require 'twilio-ruby'

# put your own credentials here
account_sid = 'YOUR_ACCOUNT_SID'
auth_token = 'YOUR_AUTH_TOKEN'

# set up a client to talk to the Twilio REST API
@client = Twilio::REST::Client.new(account_sid, auth_token)

# alternatively, you can preconfigure the client like so
Twilio.configure do |config|
  config.account_sid = account_sid
  config.auth_token = auth_token
end

# then you can create a new client without parameters
@client = Twilio::REST::Client.new

# use the client to do fun stuff like send messages or make calls!