Numerati, and everyone else who wrote me on the laptop issue:
I figured out what the problem was as to why I could not log into Seeing Arrangement from Safari or Chrome on my Mac Book Air laptop, but could do so into the very same SA account on my IPhone. It was not an SA problem, a browser problem, or an ad blocker or cookies issue. It was a simple failure to do an important software update on ioS to their new "Big Sur" software for Macs. In real life, "Big Sur" is a rugged, mountainous area of the central California coast. The new software is named after it. I realized that I had not upgraded when I checked my App updates and a few apps were not updating because I did not have the Big Sur software. Then I did the upgrade. Problem was solved completely and immediately once the upgrade was done. Was also able to quickly update the apps that had failed to update prior to the Big Sur upgrade.
I am speculating that SA must have upgraded their software so as to make it compatible with Big Sur. I was just a little behind the times on the upgrade. Thanks to the many of you who offered me helpful suggestions on the issue.