IMP is marked as authenticated, but no credentials can be found in the session.

[DocMAX]

Updated from Debian 11 to 12 and now getting this error:
Tried with PHP 7.4 but same error. Now back on PHP 8.3.

A fatal error has occurred
IMP is marked as authenticated, but no credentials can be found in the session.
in /usr/share/php/Horde/Registry.php:1679

 1. Horde_Registry::appInit() /var/www/horde/imp/index.php:19
 2. Horde_Registry->pushApp() /usr/share/php/Horde/Registry.php:298
 3. Horde_Registry->_pushAppError() /usr/share/php/Horde/Registry.php:1622
 4. Horde_Registry::appInit() /var/www/horde/imp/index.php:19
 5. Horde_Registry->pushApp() /usr/share/php/Horde/Registry.php:298
 6. Horde_Registry->callAppMethod() /usr/share/php/Horde/Registry.php:1617
 7. Horde_Registry_Application->authenticated() /usr/share/php/Horde/Registry.php:1197
 8. IMP_Application->_authenticated() /usr/share/php/Horde/Registry/Application.php:108
 9. IMP_Auth::authenticateCallback() /var/www/horde/imp/lib/Application.php:134
10. IMP_Auth::_log() /var/www/horde/imp/lib/Auth.php:252
11. IMP_Imap->__call() /var/www/horde/imp/lib/Auth.php:141

Details
The full error message is logged in Horde's log file, and is shown below only to administrators. Non-administrative users will not see error details.

Horde_Exception_PushApp Object
(
    [application] => imp
    [details] => 
    [logged] => 1
    [_logLevel:protected] => 0
    [message:protected] => IMP is marked as authenticated, but no credentials can be found in the session.
    [string:Exception:private] => 
    [code:protected] => 5
    [file:protected] => /usr/share/php/Horde/Registry.php
    [line:protected] => 1679
    [trace:Exception:private] => Array
        (
            [0] => Array
                (
                    [file] => /usr/share/php/Horde/Registry.php
                    [line] => 1622
                    [function] => _pushAppError
                    [class] => Horde_Registry
                    [type] => ->
                )

            [1] => Array
                (
                    [file] => /usr/share/php/Horde/Registry.php
                    [line] => 298
                    [function] => pushApp
                    [class] => Horde_Registry
                    [type] => ->
                )

            [2] => Array
                (
                    [file] => /var/www/horde/imp/index.php
                    [line] => 19
                    [function] => appInit
                    [class] => Horde_Registry
                    [type] => ::
                )

        )

    [previous:Exception:private] => Horde_Exception_AuthenticationFailure Object
        (
            [application] => 
            [code:protected] => 6
            [details] => 
            [logged] => 1
            [_logLevel:protected] => 0
            [message:protected] => IMP is marked as authenticated, but no credentials can be found in the session.
            [string:Exception:private] => 
            [file:protected] => /var/www/horde/imp/lib/Imap.php
            [line:protected] => 628
            [trace:Exception:private] => Array
                (
                    [0] => Array
                        (
                            [file] => /var/www/horde/imp/lib/Auth.php
                            [line] => 141
                            [function] => __call
                            [class] => IMP_Imap
                            [type] => ->
                        )

                    [1] => Array
                        (
                            [file] => /var/www/horde/imp/lib/Auth.php
                            [line] => 252
                            [function] => _log
                            [class] => IMP_Auth
                            [type] => ::
                        )

                    [2] => Array
                        (
                            [file] => /var/www/horde/imp/lib/Application.php
                            [line] => 134
                            [function] => authenticateCallback
                            [class] => IMP_Auth
                            [type] => ::
                        )

                    [3] => Array
                        (
                            [file] => /usr/share/php/Horde/Registry/Application.php
                            [line] => 108
                            [function] => _authenticated
                            [class] => IMP_Application
                            [type] => ->
                        )

                    [4] => Array
                        (
                            [file] => /usr/share/php/Horde/Registry.php
                            [line] => 1197
                            [function] => authenticated
                            [class] => Horde_Registry_Application
                            [type] => ->
                        )

                    [5] => Array
                        (
                            [file] => /usr/share/php/Horde/Registry.php
                            [line] => 1617
                            [function] => callAppMethod
                            [class] => Horde_Registry
                            [type] => ->
                        )

                    [6] => Array
                        (
                            [file] => /usr/share/php/Horde/Registry.php
                            [line] => 298
                            [function] => pushApp
                            [class] => Horde_Registry
                            [type] => ->
                        )

                    [7] => Array
                        (
                            [file] => /var/www/horde/imp/index.php
                            [line] => 19
                            [function] => appInit
                            [class] => Horde_Registry
                            [type] => ::
                        )

                )

            [previous:Exception:private] => 
        )

)