Please : don't explain what you do ,to fix issue,
Explain what you do to find the issue

You try to activate AuditLog ?

I check : it seems to work on last master, no need symbolic link.

It was all the plugins in /limesurvey/application/core/plugins/. I debugged myself and in application/models/Plugin.php I saw the path to the configuration files for plugins was pointing to /limesurvey/plugins/... So I did this adhoc solution with symbolic link and it started to work.

After a manually upgrade of Limesurvey, according to these instructions https://manual.limesurvey.org/upgrading_from_a_previous_version, I wanted to change settings in a plugin AuthLdap, therefore I went to Global Settings -> Plugin Manager and encountered immediately error message "Missing configuration for plugin AuditLog". As I understand AuditLog is on top of the plugin list.

OK :)

Upgrade from what version ?

I don't quite remember now. But it was around 4.3 I think. I upgraded because I encountered a similiar problem when I was going to change settings for AuthLdap. I went to Global Settings->Plugin Manager and got the plugin list accordingly. But as soon as I pressed AuthLdap plugin the error message was "Missing configuration for plugin AuthLdap". Then I thought maybe I should upgrade to see if it works better and on that road it was.

For information :
type of plugin set the directory : https://github.com/LimeSurvey/LimeSurvey/blob/master/application/models/Plugin.php#L25

update steps are

https://github.com/LimeSurvey/LimeSurvey/blob/ebcbc490f570ca58748eae73145e06269511e73b/application/helpers/update/updatedb_helper.php#L2830
https://github.com/LimeSurvey/LimeSurvey/blob/ebcbc490f570ca58748eae73145e06269511e73b/application/helpers/update/updatedb_helper.php#L3071
https://github.com/LimeSurvey/LimeSurvey/blob/ebcbc490f570ca58748eae73145e06269511e73b/application/helpers/update/updatedb_helper.php#L3224

AuthDB and AuditLog must be «core»

In mysql database the table lime_plugins shows type "core" for AuthDB and AuditLog and "user" for AuthLdap. But when I debugged the directory for all these plugins was pointed to /limesurvey/plugins.

I checked the upgrade from the last 4.3 to latest 4.x version and I could not reproduce the problem.
Did you maybe use a 4.4RC version in the past?

In mysql database the table lime_plugins shows type "core" for AuthDB and AuditLog and "user" for AuthLdap. But when I debugged the directory for all these plugins was pointed to /limesurvey/plugins.

Maybe related to a specific directory configuration ?

Dir set here : https://github.com/LimeSurvey/LimeSurvey/blob/5423d57d4fa289c5d54a1c5b1cdd90d7f26323b0/application/libraries/PluginManager/PluginManager.php#L35

"user" for AuthLdap

It must be core

In Plugin.php in function getDir() the following happens:
$alias is set to "webroot.plugins" and $this->plugin_type is "user" for plugin AuditLog. In mysql database the plugin_type is "core" for AuditLog. So the plugin_type is set to wrong type. I haven't yet checked how the plugin_type is set. But probably there is the error.
As I said I followed the instructions for manual upgrade and removed all files except for
/application/config/security.php
/application/config/config.php
/upload

The version before was something 4.3 as I remember I upgraded limesurvey last year in June.
The error only appears in PluginManager, otherwise Limesurvey works fine.

I can also see when I list the plugins in https://www.irf.se/limesurvey/index.php?r=admin/pluginmanager/sa/index that AuditLog and AuthLdap is marked with correct plugin_type core. But despite of that in Plugin.php plugin_type is "user" fro all plugins.

In my case, this reported error was caused by duplicate entries in the plugin table after upgrading from v4.3.19 to v5.1.2 using the instructions at https://manual.limesurvey.org/upgrading_from_a_previous_version.

id | name | active | version | load_error | load_error_message | plugin_type | priority
----+--------------------------+--------+---------+------------+--------------------+-------------+----------
1 | Authdb | 1 | 1.0.0 | 0 | | user | 0
2 | AuditLog | 0 | 1.0.0 | 0 | | user | 0
3 | AuthLDAP | 0 | 1.0.0 | 0 | | user | 0
4 | Authwebserver | 0 | 1.0.0 | 0 | | user | 0
5 | ExportSTATAxml | 0 | 1.0.0 | 0 | | user | 0
6 | ExportR | 0 | 1.0.0 | 0 | | user | 0
7 | oldUrlCompat | 0 | 1.0.1 | 0 | | user | 0

11 | AuthLDAP | 0 | 1.0.0 | 0 | | core | 0
12 | AuditLog | 0 | 1.0.0 | 0 | | core | 0
13 | Authwebserver | 0 | 1.0.0 | 0 | | core | 0
15 | ExportSTATAxml | 1 | 1.0.0 | 0 | | core | 0
14 | ExportR | 1 | 1.0.0 | 0 | | core | 0
16 | oldUrlCompat | 0 | 1.0.1 | 0 | | core | 0

Hello,
I checked this with the latest version and could not reproduce, so this is most likely fixed for good.
Therefore, I am closing this issue. If anyone still can reproduce the issue using the latest version, please feel free to re-open the issue or create a new one.
Thank you!