Thanks for the start page URL. The page and link looks fine. I suspect there's either a misconfiguration or a hiccup re. your iPhone's Safari. Things to check and try:
- Go to Settings -> Genera -l> Restrictions -> Safari. Make sure it is "allowed" or turned on (swipe to green). Exit out of settings and retry.
- Check if "Installing App" in Settings -> General -> Restrictions is allowed. If not, toggle it to on, exit out of settings and retry.
- If the above two don't apply, go to Safari settings, and clear cookies and website data. Then restart the iPhone and try again.
Please let us know what you find.