It seems that it does not support MantisBT 2.28.0.

[bubututu]

[root@MantisBT php-fpm]# tail -f www-error.log

[07-Feb-2026 14:09:26 Asia/Taipei] Undefined class constant 'MAJOR_VERSION'

/opt/mantisbt-2.28.0/vendor/guzzlehttp/guzzle/src/functions.php: 71: GuzzleHttp\Utils - :: - defaultUserAgent()

/opt/mantisbt-2.28.0/plugins/GoogleOauth/pages/assets/lib/google-api-php-client/vendor/guzzlehttp/guzzle/src/Client.php: 194: - - - - GuzzleHttp\default_user_agent()

/opt/mantisbt-2.28.0/plugins/GoogleOauth/pages/assets/lib/google-api-php-client/vendor/guzzlehttp/guzzle/src/Client.php: 75: GuzzleHttp\Client - -> - configureDefaults( { ['exceptions'] => false, ['base_uri'] => <GuzzleHttp\Psr7\Uri> ( ), ['handler'] => <GuzzleHttp\HandlerStack> ( ) } )

/opt/mantisbt-2.28.0/plugins/GoogleOauth/pages/assets/lib/google-api-php-client/src/Google/Client.php: 1058: GuzzleHttp\Client - -> - __construct( { ['exceptions'] => false, ['base_uri'] => <GuzzleHttp\Psr7\Uri> ( ), ['handler'] => <GuzzleHttp\HandlerStack> ( ) } )

/opt/mantisbt-2.28.0/plugins/GoogleOauth/pages/assets/lib/google-api-php-client/src/Google/Client.php: 1032: Google_Client - -> - createDefaultHttpClient()

/opt/mantisbt-2.28.0/plugins/GoogleOauth/pages/assets/lib/google-api-php-

client/src/Google/Client.php: 190: Google_Client - -> - getHttpClient()

/opt/mantisbt-2.28.0/plugins/GoogleOauth/pages/redirect.php: 18: Google_Client - -> - fetchAccessTokenWithAuthCode( '4/0ASc33333333DnJ4gQQQJ_m45123456789lWj-T1078doFQZ6mKAYAAAAAAAAAAQ' )

/opt/mantisbt-2.28.0/plugin.php: 74: - - - - include( '/opt/mantisbt-2.28.0/plugins/GoogleOauth/pages/redirect.php' )