Error message at checkout page

-- url of the page with the problem -- : www.ericspeanuts.com
-- HikaShop version -- : 4.6.2
-- Joomla version -- : 4.2.5
-- PHP version -- : 8
-- Browser(s) name and version -- : Version 107.0.5304.107 , edge
-- Error-message(debug-mod must be tuned on) -- : CALL TO UNDEFINED METHOD JOOMLA\CMS\APPLICATION\SITEAPPLICATION::ISADMIN()

HOME PAGE
Call stack
# Function Location
1 () JROOT\plugins\hikashoppayment\alphauserpoints\alphauserpoints.php:761
2 plgHikashoppaymentAlphauserpoints->onAfterOrderCreate() JROOT\libraries\src\Plugin\CMSPlugin.php:279
3 Joomla\CMS\Plugin\CMSPlugin->Joomla\CMS\Plugin\{closure}() JROOT\libraries\vendor\joomla\event\src\Dispatcher.php:486
4 Joomla\Event\Dispatcher->dispatch() JROOT\libraries\src\Application\EventAware.php:107
5 Joomla\CMS\Application\WebApplication->triggerEvent() JROOT\administrator\components\com_hikashop\classes\order.php:435
6 hikashopOrderClass->save() JROOT\administrator\components\com_hikashop\classes\order.php:906
7 hikashopOrderClass->createFromCart() JROOT\components\com_hikashop\controllers\checkout.php:671
8 checkoutController->confirm() JROOT\libraries\src\MVC\Controller\BaseController.php:672
9 Joomla\CMS\MVC\Controller\BaseController->execute() JROOT\administrator\components\com_hikashop\helpers\helper.php:2402
10 hikashopController->execute() JROOT\components\com_hikashop\hikashop.php:88
11 require_once() JROOT\libraries\src\Dispatcher\LegacyComponentDispatcher.php:71
12 Joomla\CMS\Dispatcher\LegacyComponentDispatcher::Joomla\CMS\Dispatcher\{closure}() JROOT\libraries\src\Dispatcher\LegacyComponentDispatcher.php:73
13 Joomla\CMS\Dispatcher\LegacyComponentDispatcher->dispatch() JROOT\libraries\src\Component\ComponentHelper.php:355
14 Joomla\CMS\Component\ComponentHelper::renderComponent() JROOT\libraries\src\Application\SiteApplication.php:200
15 Joomla\CMS\Application\SiteApplication->dispatch() JROOT\libraries\src\Application\SiteApplication.php:241
16 Joomla\CMS\Application\SiteApplication->doExecute() JROOT\libraries\src\Application\CMSApplication.php:294
17 Joomla\CMS\Application\CMSApplication->execute() JROOT\includes\app.php:61
18 require_once() JROOT\index.php:32

I upgrade my site to Joomla 4.2.5. All extensions were upgraded.
All is working only I get the error message bellow on the Hikashop checkout page.

Can you please help out.

Thank you in advance,

Eric Ware

Ok thank you, I disabled it, and it works. How can I uninstall it? I delete the plugin folder in plugins/hikashoppayment/alphauserpoints?