Hello Rocio Fernandez-Presa,
Good day!
I understand that you're experiencing this issue with the pin message button in your Outlook email. May I please know the type of account you are using. Is it M365 work or school account or a Microsoft/Personal account like Hotmail/Outlook.com?
->Can you see the pin option in the list when you right click on the email from the list?
Please verify whether the pin message feature is enabled in your Outlook settings. To do this, go to the Settings gear icon in the top right corner of your Outlook account, select "View all Outlook settings," and then click on "Mail">"Customize actions".
Under Quick actions >Make sure that the "Pin" option is checked/turned on.
->You may also try accessing your Outlook account from a different browser or device. This will help determine if the issue is specific to your current browser or device.
Looking forward to your response.
Best Regards,
Ashraf.