Hi, do you mean the frame doesn't load at all? The reCAPTCHA service is hosted by Google, and this problem can be caused by blocking Google content a little too aggressively.
Could you post this problem on the Mozilla Support site. They have a team of support volunteers to troubleshoot malfunctions with your currently installed version of Firefox, while this site is focused on idea submissions for future versions of Firefox (looking ahead anywhere from 8 weeks to many months). Here's a link to the new question form (for Windows/Mac/Linux): https://mzl.la/3y1vQUQ
