Hey, @harish_6373. Welcome to the Lightroom Community. I'll help you figure this out. I couldn't find a active subscription on the email you've used for Community. Have you installed Lightroom on this device for the first time, or have you updated the app recently?
In the past, this error has been linked to session timeouts. Please keep the app open for longer than 5 minutes before you restart the app.
Also, try keeping the iPhone connected to WiFi.
Let me know how it goes. Thanks! Sameer K
(Type '@' and type my name to mention me when you reply)
p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.