Magento 2 Invalid Form Key. Please refresh the page

Question

After Upgrading My Site to Magento version 2.4.3 I am facing this issue on my admin login at 2FA Login screen.

Please Help me About this why its showing the invalid form key.

Answer 1

Magento 2.4.3 has a known bug causing this problem. One user reported your exact problem. From that Github issue, this solution is reported to work until Magento patches this in a future release. I'm unable to paste it here as it doesn't appear to play nice with StackExchange formatting tools, but those links should get you to a solution.

Answer 2

Run below command in terminal Magento root path :

bin/magento module:disable Magento_TwoFactorAuth
bin/magento cache:flush 

Answer 3

You have to change default Magento's File

Go to , Magento/Backend/App/Action/Plugin/Authentication.php

find protected function _redirectIfNeededAfterLogin() function

And Replace With Below Code :

 protected function _redirectIfNeededAfterLogin(\Magento\Framework\App\RequestInterface $request)
{
    $requestUri = null;

    // Checks, whether secret key is required for admin access or request uri is explicitly set
    if ($this->_url->useSecretKey()) {
        $requestParts = strpos(trim($request->getRequestUri(), '/'), $request->getFrontName()) === 0 ?
            explode('/', trim($request->getRequestUri(), '/'), 4) :
            explode('/', trim($request->getRequestUri(), '/'), 3);
        if (($key = array_search($request->getFrontName(), $requestParts)) !== false) {
            unset($requestParts[$key]);
        }
        $requestParams = $request->getParams();
        unset($requestParams['key'], $requestParams['form_key']);
        $requestUri = $this->_url->getUrl(implode('/', $requestParts), $requestParams);
    } elseif ($request) {
        $requestUri = $request->getRequestUri();
    }

    if (!$requestUri) {
        return false;
    }

    $this->_response->setRedirect($requestUri);
    $this->_actionFlag->set('', \Magento\Framework\App\ActionInterface::FLAG_NO_DISPATCH, true);
    return true;
}

Changes in Default Magento files is not a god practice, until you have to wait Magento official to fix this bug...Or Use this Solution Its Working in my case

Ref : Github