Troubleshooting Third-Party Integrations

Troubleshooting Integrations

Postcards connects to several third-party services, such as Mailchimp, HubSpot, Constant Contact, Klaviyo, and others. The integrations are designed to work seamlessly, but every now and then issues can pop up; usually because of permission settings, account limits, or temporary problems on the third-party side. This article walks through the most common issues and how to resolve them.

Common integration issues

Authentication errors, like invalid credentials or expired tokens
Templates failing to appear in the connected service after export
Permission or access restrictions on the third-party account
API rate limits or usage caps based on the third-party plan
Images not showing up in the imported template
HTML coming through minified or formatted differently than expected

Troubleshooting steps

1. Reconnect the integration

Most authentication issues, expired tokens, outdated permissions, or sync failures can get resolved by disconnecting and reconnecting the integration. To do this:

Open any project in Postcards and click Export in the top right corner and select Send to email platform (the integrations menu).

Find the integration you're having trouble with in the list, and hover your mouse over it, a small pencil icon will appear.

Click the pencil icon, and a popup will appear with a Remove option.
Click Remove to disconnect the integration from Postcards.

Now reconnect it the same way you did originally, click the + button next to the integration, log in to the service, and grant access again.

This usually clears up authentication and permission issues caused by tokens expiring or being revoked on the third-party side.

2. Confirm account permissions

Make sure the third-party account you're connecting with has the right permissions to access templates, APIs, or marketing tools on that platform. Limited-access roles, sub-accounts, or restricted user permissions on the service's side can prevent the integration from working properly even when the credentials are correct.

3. Check for error messages during export

If an export fails, Postcards will usually show a brief error message at the moment it happens. The message often points to the source of the problem, for example, an authentication error, a missing permission, or a service-side limitation. Reading that message closely is often the fastest way to figure out where the issue actually lies.

4. Review service status and API limits

If the integration was working before and suddenly isn't, check the third-party service's status page for outages or maintenance windows. Also confirm you haven't hit a usage limit; some platforms cap API requests, template imports, or campaigns on lower-tier or free plans (Mailchimp, HubSpot, and Klaviyo all have plan-based limits).

A note on expected warnings

Not every warning you see in a third-party platform is an actual error. For example, HubSpot may show warnings about a missing dnd_area_stylesheet after importing, this is a non-blocking notice and the template still works as expected. If you see warnings but the template renders and sends correctly, it's usually safe to proceed.

Some ESPs also tend to re-wrap or modify the HTML on import, which can sometimes cause subtle differences in how the template looks or behaves compared to what you saw in Postcards. Unfortunately this is on the ESP's side and not something we can fully control. If you do notice any discrepancies, the best first step is to re-import the unedited HTML rather than pasting code manually or use the direct integration export path if your ESP supports it.

When to contact the third-party support team

If you've confirmed everything is correct on your end and the issue persists, it may be a platform-side problem. Reach out to the third-party service's support team when:

Authorization requests are rejected even with valid credentials
The service is returning unexpected API errors
There's confirmed platform downtime or service issues on their end

When contacting them, share any error messages and timestamps to speed up their investigation.

When to contact Postcards support

If you're not sure whether the problem is on Postcards' side or the third-party's, reach out to us and we'll help track it down. To make things faster, please include:

The name of the integration you're using
A short description of the issue
Any error messages you received
The steps you've already tried

We'll help figure out whether the issue is on our side or whether it needs to be escalated to the third-party team.