Error with click activity

Hi, I built an automation task last month and tested it many times and it was working fine. I am trying to run it again but it keeps failing at some of the click activities with the following error:

Click ‘page tab Posts’: Cannot find the UI element corresponding to this selector:

The thing is if I comment that activity and add a similar one instead, it works!

I don’t understand what’s going on. Could you please help?

Many thanks in advance,
Maha