In WHMCS v7.8, Time Based Tokens no longer require a paid subscription, making this feature free to use.

Effective 28th August 2019 all billing for Time Based Tokens services will cease. You will no longer be charged for this service and any outstanding invoices for this services cancelled.

Please cancel PayPal subscriptions for this service via the PayPal website.

Users who pay for time-based tokens on a yearly basis will automatically receive a pro-rated credit for any remaining term. 

For more information on the improvements to Two Factor Authentication and billing practicalities, please refer to this blog post: https://blog.whmcs.com/133567/announcing-time-based-tokens-are-becoming-free