Multiple WordPress support threads document the same frustrating pattern with CF7 to MailerLite integrations. Subscribers either do not appear at all, or they land in the general subscribers list instead of the specific group selected in the plugin settings. No error is shown on the form. The submission appears to succeed.
Four distinct causes produce this identical symptom. Here is each one with exactly what to check.
Cause 1: Double Opt-In Is Enabled on the Group
This was the resolution in two separate forum threads. One was closed with just this note: "The issue was solved through email. Double opt-in option was on."
When double opt-in is enabled on a MailerLite group, subscribers added via API are placed in a pending state until they confirm their email. They do not appear in the group as active subscribers. From the WordPress side, the integration looks like it did nothing — the person is not in the group.
The person was added. They are pending. They just do not appear as active subscribers until they click the confirmation email.
Check this first: In your MailerLite account, go to Subscribers, then Groups. Open the group your CF7 integration is adding to. Click Settings. Look for the double opt-in setting. If it is enabled and you want subscribers added immediately without a confirmation step, disable it.
Alternatively, if you need double opt-in for GDPR compliance, understand that this is working correctly — the subscriber will appear in the group after they confirm. Set up MailerLite to send the confirmation email correctly and check the Unconfirmed tab in the group to see pending subscribers.
Cause 2: Classic API Key vs New API Key
MailerLite migrated their API in 2022-2023 from a "Classic" version to a "New" version. These are not interchangeable. Classic API keys (generated in the old MailerLite dashboard) do not work with New API endpoints, and vice versa.
A forum user reported that data was getting through to MailerLite but the subscriber was not being added to the group. The plugin was using the MailerLite Classic API SDK while their MailerLite account was on the New platform.
How to tell which you have:
- If your MailerLite account URL is
app.mailerlite.com— you are on the New platform. You need a New API key. - If your account URL is
app.mailerlite.com/classicor you signed up before 2022 and have not migrated — you may still be on Classic.
Generate the correct API key:
- New MailerLite: go to Integrations, then API, then create a token
- Classic MailerLite: go to Integrations, then Developer API
If the plugin you are using was last updated before 2023, it is likely using the Classic API SDK and will not work correctly with a New API key.
Cause 3: CleanTalk or Spam Plugin Conflicting With the Submission Hook
One forum thread documented a specific CleanTalk interaction. The site owner was using Contact Form 7 Connector for MailerLite sign-ups. With CleanTalk enabled, every submission returned "There was an error trying to send your message" and no subscriber was added. Disabling CleanTalk fixed it immediately.
The CleanTalk dashboard showed all events as "approved" — no spam detected. But something in CleanTalk's processing was interfering with the CF7 hook execution before the MailerLite integration could fire.
If you are using CleanTalk:
- Temporarily disable CleanTalk and test the form
- If subscribers are added correctly without CleanTalk, the conflict is confirmed
- In CleanTalk settings, look for a "Forms to Protect" whitelist and add your CF7 form
- Also check "Protect Logged-in Users" — disable it if you are testing while logged in
The same conflict can occur with other aggressive spam protection plugins (Cerber Security, WP Cerber) that intercept form submissions before CF7's hooks complete.
Cause 4: Plugin Not Updated for MailerLite's API Migration
A forum user trying the CF7 Connector MailerLite add-on reported subscribers were not being added to the correct group. A community member confirmed: "Looks like the plugin wasn't updated to be compatible with the latest version of MailerLite." The user switched to AFI (Advanced Form Integration) and it worked immediately with the same API key and group settings.
This is the structural problem with dedicated integration plugins that depend on a specific email platform's API: when the platform migrates their API, the plugin must be updated to match. If the plugin author is slow to update or has abandoned the plugin, users are left with an integration that authenticates successfully but fails silently on group assignment.
Check: Look at the plugin's last updated date in WordPress admin and compare it to MailerLite's API migration announcement (2022-2023). If the plugin predates the migration and has not been updated since, it is running against a deprecated API.
Calling MailerLite's New API Directly
The MailerLite New API endpoint for adding a subscriber to a group:
POST https://connect.mailerlite.com/api/subscribers
Authorization: Bearer YOUR_NEW_API_TOKEN
Content-Type: application/json
Accept: application/json
{
"email": "jane@example.com",
"fields": {
"name": "Jane Smith",
"last_name": ""
},
"groups": ["GROUP_ID_HERE"],
"status": "active"
}
Get your group IDs:
curl "https://connect.mailerlite.com/api/groups" \
-H "Authorization: Bearer YOUR_TOKEN" \
-H "Accept: application/json"
The id field in each group object is what goes in the groups array.
Contact Form to API calls this endpoint directly from the WordPress dashboard. You configure the MailerLite New API endpoint, add your token as a Bearer header, and map your CF7 fields to the subscriber payload. The group ID goes directly in the groups array in your JSON body — no plugin middleware that might be running against the old Classic API.
Quick Diagnosis
| Symptom | Most Likely Cause |
|---|---|
| Subscriber appears in Unconfirmed tab | Double opt-in enabled on the group |
| Subscriber in all subscribers but not in group | Double opt-in enabled OR group ID wrong |
| No subscriber created, no error | CleanTalk or spam plugin conflict |
| Subscriber not added, error in debug log | Classic API key with New platform (or vice versa) |
| Was working, stopped after MailerLite update | Plugin not updated for API migration |
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