Hi,
I had this issue and was able to fix it. It could be one of two things,[br]
1. Your iCloud is too full (this is what happened to me) I went into the settings clicked on my profile, then iCloud then managed my data, and removed all of my photos from iCloud. So just back up your stuff and either add more storage or delete the unnecessary items from your iCloud. Just free up some space in there somehow.[br]
2. (Saw someone said this worked for them on reddit) find a way to accept iClouds new Terms and Conditions. I’m not sure where to find this but someone said they noticed they hadn’t accepted the t&c and once they did they were able to share notes again.
Hope this helps :)