sync calendar

Hi All

I am having issues with syncing my calendars, I am using Big Sur

The problem is that if i entered something onto the calendar on my MacBook it shows up on my phone and iPad, however if i enter something on my phone it will not sync to iPad or MacBook.

I have different calendar entries for different items colour coded, and looking at the phone it has two accounts one says iPhone the other is my email address which is linked to iCloud, it will only allow a tick next to the calendar event that i wish to use eg i have events, charity, holiday, other , mine so if i put a tick against other on my email account calendar it shows on my MacBook and iPad but as soon as i change to a different calendar event say holiday the things that were showing in other disappear

any suggestion please as i am missing being at places etc

many thanks

eon