Currently doing a user test but seems that people with an iphone 6,7 or 8 are not able to load the prototype.
I think this is a bug and you need to report it to Figma support team via the bug report form.
Same problem here, iphone SE and iphone 8. I can’t open the prototype link with any browser (safari, chrome, Duckduckgo).
In the past I could open, but since some time no luck.