[Bug] Error „The plugin ActivityLog is not enabled“ Matomo 5.x / TagManager

[JidWictut]

What happened?

When accessing Matomo dashboards or loading the TagManager module, the following error appears in the log:
ERROR Piwik\ExceptionHandler [...] Uncaught exception: /core/FrontController.php(502): The plugin ActivityLog is not enabled. You can activate the plugin on Settings > Plugins page in Matomo. [Query: ?action=index&module=ActivityLog, CLI mode: 0]

What should happen?

Error appears regularly in matomo.log.

ActivityLog plugin was never installed (paid version).

Dashboard or TagManager functions otherwise run normally.

How can this be reproduced?

The error is caused by the TagManager plugin.

In plugins/TagManager/Activity/BaseActivity.php, there is the following line:

use Piwik\Plugins\ActivityLog\Activity\Activity;

Since the ActivityLog plugin is not installed, PHP tries to find the namespace when loading this class, fails, and throws the error.

Other plugins or dashboards are not affected.

Matomo version

5.5.0

PHP version

8.3

Server operating system

No response

What browsers are you seeing the problem on?

No response

Computer operating system

No response

Relevant log output

Validations

• Read our Contributing Guidelines.
• Follow our Security Policy.
• Check that there isn't already an issue that reports the same bug to avoid creating duplicates.
• The provided steps to reproduce is a minimal reproducible of the Bug.

[michalkleiner]

Declaring use of an inaccessible class should be fine, as long as it's not used, so the problem is likely somewhere else other than the use line.

[michalkleiner]

In your issue description, you mentions the query, which tries to, likely, access the plugin.

[JidWictut]

Thanks for your reply.
Why is a plugin that is NOT installed and NOT FREE causing errors?
Why is this plugin even being queried in a core file?

[sgiehl]

That for sure should not be the case. We need to figure out where and why that happens and ensure that gets fixed.
Are you able to describe more detailed when exactly that call is triggered? Is it maybe visible as failed request in the browser console?

[JidWictut]

The error seems to appear sporadically. I have entries in the log file at different times and on different days.

[sgiehl]

Are you able to confirm that those requests are triggered by real users of your Matomo instance and occur somewhere visible in Matomo?
Those errors could in theory also occur if someone directly tries to open the ActivityLog URL without the plugin being installed.

[JidWictut]

Summary
Matomo occasionally throws an exception in the log stating that the ActivityLog plugin is not enabled, even though it is not installed at all.
The error appears sporadically and seems to be triggered by internal references to module=ActivityLog within the Matomo core or TagManager plugin.

Error message
ERROR Piwik\ExceptionHandler[2025-11-04 21:15:44 UTC] [cca71]
Uncaught exception: /core/FrontController.php(502):
The plugin ActivityLog is not enabled.
You can activate the plugin on Settings > Plugins page in Matomo.
[Query: ?action=index&module=ActivityLog, CLI mode: 0]

Environment
Matomo version: 5.5.1
PHP version: 8.x
Database: MariaDB/MySQL
Server OS: Linux (shared hosting)
Plugins enabled: Core + TagManager + CustomDimensions + several standard plugins
ActivityLog not installed (never was)

Steps to reproduce (sporadic)

Run Matomo 5.5.1 with the TagManager plugin enabled.
Do not install or enable the ActivityLog plugin.
Occasionally, during backend navigation or after cache rebuilds, an error appears in the Matomo log:
The plugin ActivityLog is not enabled. You can activate the plugin on Settings > Plugins page in Matomo.
The issue may occur once every few hours or after certain page loads (e.g., Dashboard or TagManager UI).

Expected behavior
Matomo should not attempt to load module=ActivityLog when the ActivityLog plugin is not installed.

Actual behavior
Matomo sporadically triggers a front controller request to ?module=ActivityLog&action=index,
causing an uncaught exception in /core/FrontController.php.

Temporary workaround
Installing a dummy placeholder plugin named DummyActivityLog (empty module providing Piwik\Plugins\ActivityLog\Activity\Activity class) fully prevents the error.
However, the plugin itself shows as “not compatible with Matomo 5.5.1”.

Notes
No database entries reference ActivityLog.
The issue seems linked to a residual internal reference (possibly in TagManager or menu registration).
The problem may only appear after plugin activation/deactivation or cache rebuilds.
Please consider adding a safe check before routing to ActivityLog in FrontController or related menu definitions.

[sgiehl]

@JidWictut I have searched through the whole core and tagmanager code base. There is only one indirect reference to the ActivityLog plugin. In case the plugin is enabled there will be an additional message shown in the user management, on the page where you can give someone super user access.
But this is also only a link, that you would need to click. So there isn't anything that would trigger automated calls to that plugin within the code base. So in case you have that error in your log file, that most likely means that someone tries querying it directly.
In that case that would actually be sort of expected behaviour. If you provide a module parameter in the url, with a value that doesn't match an existing plugin, it will show up as an error in the log.

[wbdb]

Log: /var/log/plesk-php83-fpm/error.log
[20-Jan-2026 13:10:18] WARNING: [pool example.com] child 1782463 said into stderr: "PHP message: [example.com] Error in Matomo: The plugin ActivityLog is not enabled. You can activate the plugin on Settings > Plugins page in Matomo."

grep -nEi 'ActivityLog|activitylog' /var/www/vhosts/system/example.com/logs/proxy_access_log | tail -n 50

I don't have the plugin active either. There are no access log entries. Matomo-Version: 5.6.2.

[sgiehl]

With #23891 we have changed how such errors are handled. If they are caused by direct requests, that are expected to fail, when the plugin is not installed, the error will no longer be logged as warning.
I'll close this issue for now. Let us know if you still see such errors after updating to Matomo 5.7.0 (which will be released the next weeks)