Hi there,
If your Xbox characters are your active characters you will not be able to access any Steam characters unless you deactivate Cross Save. Please note that doing so will put you in a 90-day lockout before you can reactivate Cross Save.
If you are unable to deactivate Cross Save, please fill out our Cross Save contact form.
https://www.bungie.net/en/Help/Troubleshoot?oid=48099