Dear Anna Pavnica
Thanks for choosing Microsoft Community.
Based on your description, I know the sceanrio you met. For this, please be kindly to try the following suggestions and check if these can make any difference.
Open the area in Outlook that had the error message and perform the following steps. If you do not know which area this is, please repeat the steps for each area of Outlook (Contacts, Calendar and Tasks):
- Change the Current View to View by Category; you will see a list of categories
- Click on the plus sign to the left of the category name to view the items in the category
- You will see an icon to the left of each item; look down the list of items for a "crossed-swords" icon or other warning icons
- Double-click each item that has one of these items to resolve the problem
If this doesn't work ,please try the following suggestions.
Hope the suggestions above can help you. If this persists, please be kindly to provide me the screenshot about your Outlook client. I will continue to test for you and help you based on the information you provide. Your understanding and co-operation are highly appreciated.
Thanks for your precious time. Have a nice day.
Sincerely,
Katherine