Change Planner logo

In the Planner :

1. I click 3 dots > member .....forward me to Outlook online.

2. I select the group that I want to change the logo

3. I click About and Edit 

4. I could change the logo, it appears correctly

5. But when I go to Planner, the logo remains the same, even after many times refresh.

Any other solutions and thanks

Note : I am member of admin