How do I turn on cookies on my iPad?

As you have already marked your own reply as “best answer”, you have presumably found the answer for yourself.

In case you haven’t, but have instead been impatient in waiting for a reply, you may need to understand that while third-party cookies are intentionally disabled, first-party cookies are enabled by default - unless you have blocked them in iPad settings:

Settings > Safari > Block All Cookies - set to OFF

Set to ON only if you wish to unconditionally block all cookies.