Thanks for being willing to help. Issue has been resolved! Someone from Cloudflare got back to me* saying that the old ecommerce solution (LightSpeed) had created a Custom Hostname certificate with Cloudflare that is preventing shopify from resolving properly. I’ve submitted a ticket to LightSpeed about it and hope they will get back to me. When my client’s website stopped working a couple months ago they were not responsive to her, so … fingers crossed.
*I signed up for the free cloudflare account and when I tried to contact support they redirected me to this community, saying the usual customer support requires a paid plan. But thankfully one of my requests reached someone who could explain the situation to me and now I know what’s going on and what the next step is.
Thanks again.