Recaptcha not appearing with Contact Form 7 on some browsers

I recently updated a client’s WP site that was originally using Really Simple Captcha with Contact Form 7. But it was no longer working so I followed the instructions for using Recaptcha instead. I have tested this page repeatedly and have no problems on my (Apple) devices, but my client and several ‘friends’ are having problems with Really Simple still trying to make its appearance. I uninstalled RS and deleted it and this is still what they are getting at the bottom of the contact form (despite several attempts to clear their caches):

Input this code: To use CAPTCHA, you need Really Simple CAPTCHA plugin installed.

https://sewingreferralnetwork.com/contact/