The pre-chat form doesn't show up even though I have already enabled it.
If the pre-chat form doesn't show, ensure there is an agent online on the live chat.
If you are using messaging, the pre-chat form isn't available for use.
As a workaround, create a custom conversation flow using the bot builder to automate your messages and collect the information of your visitor before sending them to an agent.
Using the Transfer to agent step, you can add ticket fields to the flow to require users to enter their information.
See the image below as an example flow that asks the customer for their name and email address before transferring the conversation to an agent.
If you still want to use the pre-chat form, disabling Zendesk messaging is your best option.