Reinstall to Enable iMessage
If you installed the marketplace app before iMessage support was added, you won't see iMessage as a channel in Conversations until you reinstall it. This short guide walks through the reinstall flow so the iMessage custom provider becomes available on your sub-account.
Conversation providers are registered when the marketplace app is installed on a sub-account. Uninstalling and reinstalling refreshes the provider list, which is what makes iMessage show up alongside your other channels.
Step 1: Uninstall the Existing App
Open the marketplace app's page in your CRM and click Uninstall in the top right.

Step 2: Reinstall the App
Once the app shows as uninstalled, click Install to add it back.

Step 3: Select Your Sub-Account
Pick the sub-account(s) you want iMessage enabled on, then click Continue.

Step 4: Confirm iMessage Is Now a Conversation Provider
Scroll down the app details page to the Conversation Provider section — you should now see iMessage listed alongside your existing providers.

Step 5: Use iMessage in Conversations
Head into Conversations in your sub-account — iMessage is now selectable as a channel from the message composer dropdown.

Your sub-account now has iMessage as a native conversation channel. If you haven't yet set up the Mac sync app, head back to the iMessage Full Setup guide to finish the rest of the flow.