Delete the app from your phone and reinstall the latest version of the Calendar app from the App or Play Store. You should now log in again
When scheduling activity: after the + sign comes the question, “Allow Calendar to record audio”. Here, you can/should click on “While using the app”.
Under Media, when the selector (None) is clicked and “Photo” > “Select photo” is chosen, the question “Allow Calendar to access photos and media on your device?” appears.
Now “Allow” can/should be clicked.
After this, the photo gallery opens.