Thank you, @paul2009. I never saw your helpful reply because it automatically went to our Squarespace email, not my work email (firstname.lastname@example.org). (I'm not an admin for that email.)
It's a relief to know that we have a 7.1 site and the problem is NOT with Ajax Loading, as suggested by our donor management software product Bloomerang customer support.
The issue we're experiencing is that some people cannot see the credit card form on our donate page. Others, like me, can. (See attached screenshots.) I checked with those who cannot see the form and they, like me, were using Chrome. (The URL for our donate page is https://www.epatt.org/donate.) Any idea what's happening? Our vendor Bloomerang says they cannot help glitches that show up on Squarespace.
Please email my work email, if possible: email@example.com. Thank you, in advance, for any light you can shed on this issue.