Fax.Plus MCP Troubleshooting

When Fax.Plus MCP does not do what you expect in Claude or ChatGPT, the cause is usually one of a few things: the sign-in did not finish, the connector is not on for the chat, a tool is blocked, or the account cannot use MCP. Find your problem below and work through the checks in order.

Start with a quick check

Two prompts that tell you most of what you need. Both are read-only.

I see no Fax.Plus tools after signing in

1. Return to your assistant and complete the Fax.Plus sign-in if it is still open.
2. Refresh the connection. In Claude, reopen the connector under Settings → Connectors. In ChatGPT, open the app and select Refresh.
3. Check the tool permissions. Tools set to Blocked cannot be used.

Claude does not use Fax.Plus in my chat

Connecting the connector and using it in a chat are separate steps.

1. In the chat, select + → Connectors and make sure FaxPlus is on.
2. Check the tool permissions: tools set to Blocked cannot run, and tools set to Needs approval wait for your confirmation.
3. If FaxPlus is missing from the list, go to Settings → Connectors and confirm that it shows as connected.

ChatGPT does not use Fax.Plus in my chat

1. Select FaxPlus from the available apps or tools in the chat, or type @ and choose it.
2. If it is not listed, open the app, sign in again and select Refresh.
3. Available options depend on your ChatGPT plan and workspace settings. Adding Fax.Plus as a custom MCP app uses Developer mode; see the ChatGPT setup guide.

The connector does not show up inside a Project

If a connector does not show up inside a project chat in your client, open a regular chat instead and paste your desk instructions as your first message. See Set up a fax desk with AI.

The assistant says an action is not available or not allowed

• Your plan: Fax.Plus MCP works on paid plans from Basic. Ask “What Fax.Plus plan am I on?” to check, or see check your plan with AI.
• Your security settings: MCP is unavailable for accounts with Advanced Security Controls, including HIPAA and PHIPA configurations.
• Your role: team tools, such as members and number assignment, are for corporate accounts and may need an admin or owner role.
• REST-only actions: buying or releasing numbers, balance, team invitations and roles, account settings, webhooks and bulk deletion are not MCP tools. See MCP or REST API.

The Fax.Plus upload window does not open when I send

Sending a fax from a chat goes through the Fax.Plus upload window, where you choose the file. If your client cannot show it, the assistant tells you so. In that case, send the document from the Fax.Plus web app, the mobile app or Email to Fax, and use the assistant afterwards to check delivery and get the confirmation report.

I got an error or no answer after a send or a change

Do not assume the action failed. Check the current state first:

• After a send or a resend, ask for your outbox and your sent faxes before you send again, so the same fax is not sent twice.
• After a change, such as a comment, a contact or a group, ask the assistant to show the item again.

A lookup returned nothing

A lookup that succeeds with no entries means nothing matches the request. A tool that is unavailable or reports a failure means the lookup did not run; it does not mean you have no faxes, numbers or contacts. Check the connection and the account, then try again.

The assistant shows the wrong account

The assistant works with the account you signed in with. If you see the wrong faxes or numbers, disconnect the connector in your client and connect again with the right Fax.Plus account.

Related

Setup guides for Claude and ChatGPT, Set up a fax desk with AI, and the MCP setup hub.