Form doesn't show up in client's browser

I’ve created a password protected page with a questionnaire for clients. The site shows up perfectly fine when I open it in safari, chrome and brave browser, but it doesn’t in my client’s browser (see attached photos to compare the two). Whilst the form itself doesn’t show, she can see the submit button hidden behind my navbar when she scrolls up. Also, when she tries to fill in the form in my footer (for newsletter), it won’t show what she typed in - only shows the cursor moving.

I have a hunch this might be because of her cookie settings, but am not sure. Judging from her photo, she’s using safari as a browser. She’s rather technically illiterate, so I’m not sure asking what kind of cookie settings she has will lead anywhere.

Here’s my read only link

What site looks like in my browsers:

What site looks like in her browser: