Hello @Nofar Cohen
Welcome to the community!
The policy for resetting master password is not retroactive users that are part of the business need to log out and log back in to be able to create a sharing key. You can find more here: https://support.lastpass.com/s/document-item?language=en_US&_LANG=enus&bundleId=lastpass&topicId=LastPass%2Ftroubleshoot_lastpass_no_mp_reset_option.html and https://support.lastpass.com/s/document-item?language=en_US&bundleId=lastpass&topicId=LastPass/reset-user-master-password-super-admin.html&_LANG=enus
Kind Regards,
Alejandra
LastPass Tech Support