How can I fix shared Notes not syncing my colleague’s changes to my iPhone?

I have notes shared with a colleague. She can see the changes, but I can't see hers. Synchronization isn't working on my end. However, I've increased my iCloud storage space, installed the latest iOS update, and made an iCloud backup. What should I do? Thank you.

[Re-Titled by Moderator]

Original Title: shared notes synchronization problem