My name is Rae, and I work for Shopify.
Thank you for letting us know about the troubles you're having with accepting the terms and conditions for Facebook. I can certainly help look into this further!
As a first troubleshooting step, I recommend ensuring that all Facebook Shop and Instagram Shopping features are completely set up on your account. You can check this by logging in to your Shopify admin, visiting the 'Facebook' section, and clicking the 'Overview' tab. If you see any buttons that say 'Continue setup' here, please select those and work through the steps required. Once that's complete, you should be able to accept the terms and conditions correctly in the 'Settings > Commerce settings' section of the Facebook channel.
However, if that doesn't resolve things, I suggest turning off cross-site tracking on your browser, as this has been known to work for other merchants. To turn off this setting in Chrome, follow these steps:
If you prefer to use Safari instead, you can turn off this setting by completing these steps:
Once you complete this, please head back into the 'Facebook' section of your Shopify admin and try to accept the terms and conditions once again. If you're still encountering troubles with this, feel free to reply back to me here for more assistance.
I look forward to hearing how this goes!