Magento 2 Community Edition software.

After updating to 2.4.1 from 2.3.5

Problem:

The "Proceed to Checkout" button doesn't work on the minicart, and on the Cart page.

Also: you cannot log in to the Admin backend as there is a Recaptcha error

Solution:

They are part of the same thing: the Google recaptcha script has broken and needs resetting.

1. Get into admin:

using ssh and the command line in your store folder. execute the command:

php bin/magento security:recaptcha:disable-for-user-login

this will disable the ReCaptcha for admin login. Log in to admin, go to the recaptcha section:

2. Turn off Recaptcha temporarily

Stores > Configuration > Security > Google Recaptcha Storefront

Under 'Storefront' turn recaptcha to "off" in each section

Save.

Refresh the Cache as suggested.

Check your "Proceed to Checkout" buttons now work. Hooray.

3. Turn Recaptcha back on

Stores > Configuration > Security > Google Recaptcha Storefront / Google Recaptcha Admin Panel

Re-enter your recaptcha keys in both sections, re-enable recaptcha where you want it.