This is due to the API keys in your Stripe account being expired and is out of our control, however it’s easy to resolve this by following these steps as provided by Stripe Support:
Login your Stripe Dashboard : https://dashboard.stripe.com/developers
Select ‘Developers’ on the left of the page, then click ‘API Keys.’
Select the ‘•••’ button on the right of the API key and Select ‘Roll key…’
Select when you’d like your old keys to be expired and enter your password to confirm. Here’s a link with more specifics: https://stripe.com/docs/keys
Once you have completed the above steps, please uninstall Charge for Stripe and then reinstall it (just to ensure you’re prompted to complete the initial setup process again) and you should be able to connect your Stripe account all ok, however if you still encounter this issue after following these steps, please contact us so we can assist you further.