Anki won't open on iPhone

I have been using anki for a few years now, but today, when I try to open it on my iPhone, the anki screen comes up and then immediately vanishes. It simply will not open. Has anyone had a similar issue? I have updated my phone and restarted it numerous times.

You have quite an old AnkiMobile version on your phone. Have you tried updating to the latest version in the app store?